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Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer Egyptian Journal of Petroleum xxx (2017) xxx–xxx Contents lists available at Scie[.]
Egyptian Journal of Petroleum xxx (2017) xxx–xxx Contents lists available at ScienceDirect Egyptian Journal of Petroleum journal homepage: www.sciencedirect.com Full Length Article Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer Ahmed S Mohammed Department of Civil Engineering, University of Sulaimani, Iraq-Kurdistan Region-Sulaimani, Iraq a r t i c l e i n f o Article history: Received 11 November 2016 Revised 13 January 2017 Accepted 17 January 2017 Available online xxxx Keywords: Bentonite Polymer (Guar gum) Electrical resistivity Rheological properties Temperature Modeling a b s t r a c t In this study, the electrical resistivity and rheological properties of a water-based bentonite clay drilling mud modified with the lightweight polymer (guar gum) under various temperature were investigated Based on the experimental and analytical study, the electrical resistivity was identified as the sensing property of the bentonite drilling mud so that the changes in the properties can be monitored in realtime during the construction The bentonite contents in the drilling muds were varied up to 8% by the weight of water and temperature was varied from 25 °C to 85 °C The guar gum content (GG%) was varied between 0% and 1% by the weight of the drilling mud to modify the rheological properties and enhance the sensing electrical resistivity of the drilling mud The guar gum and bentonite clay were characterized using thermal gravimetric analysis (TGA) The total weight loss at 800 °C for the bentonite decreased from 12.96% to 0.7%, about 95% reduction, when the bentonite was mixed with 1% of guar gum The results also showed that 1% guar gum decreased the electrical resistivity of the drilling mud from 50% to 90% based on the bentonite content and the temperature of the drilling mud The guar gum modification increased the yield point (YP) and plastic viscosity (PV) by 58% to 230% and 44% to 77% respectively based on the bentonite content and temperature of the drilling mud The rheological properties of the drilling muds have been correlated to the electrical resistivity of the drilling mud using nonlinear power and hyperbolic relationships The model predictions agreed well with the experimental results Hence the performance of the bentonite drilling muds with and without guar gum can be characterized based on the electrical resistivity which can be monitored real-time in the field Ó 2017 Egyptian Petroleum Research Institute Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Introduction Water-bentonite clay suspensions have been used in the oil, gas and geothermal drilling industry for decades Multi-functional drilling muds are required to transport the rock cuttings to the surface, lubricate and cool the drill bit and apply hydrostatic pressure in the wellbore to ensure well safety The deeper wells that are being drilled calls for more advanced drilling fluids because of the changes in pressure, temperature and geology formations The drilling fluid can react with certain types of formation or the pressure can cause the rock to crack, leading to massive loss of fluid into the formation [1,2] Hence there needs to not only enhance the performance of bentonite based drilling mud but also monitor the performance of the drilling muds during the drilling operations [3] Bentonite is a type of clay consisting mainly of a hydrous silicate of aluminum; its color varies from gray to brown Bentonites have formed by weathering of volcanic tuff and ash and consist mainly Peer review under responsibility of Egyptian Petroleum Research Institute E-mail address: ahmed.mohammed@univsul.edu.iq of montmorillonite [(Al,Mg)2(OH)2(Si,Al)4O10(Ca)x on H2O] and contain varying amounts of other minerals such as quartz (SiO2) and calcium and sodium feldspar [(CaAl2Si2O8),(NaAl3Si2O8)] [4] In general, the bentonite is classified into two types; Nabentonite, which has a high swelling capacity, and Ca-bentonite, which is a non-swelling clay and forms colloidal very quickly in water Bentonite suspensions are widely used in oil and gas industry because of their exceptional rheological properties [5] Generally, the flow of bentonite dispersions is very sensitive to the Na+/Ca+2 ratio The rheological measurements of bentonite dispersions, an important route to revealing the flow and deformation behaviors of materials, cannot only improve the formulation process of commercial products but can also be very important in design and process evaluation, quality control, and storage stability [6] The main function of the bentonite is to increase the viscosity of the mud and to reduce the fluid loss to the formation A good quality bentonite should contain mainly montmorillonite [7] Bentonite often contains other clay minerals such as illite and kaolinite and non-clay components such as quartz and feldspar [8] Based on 72 data collected from the literature (CIGMAT data base) the http://dx.doi.org/10.1016/j.ejpe.2017.01.002 1110-0621/Ó 2017 Egyptian Petroleum Research Institute Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx amount of bentonite used in water based drilling muds varied from 0.5 to 14% (by weight of water) Over 50% of the studies used up to 6% of bentonite in water based drilling mud [9] Guar gum is defined as having the particle size in the range of to 100 nm Montmorillonite (MT) based guar gum is chemically a hydrated sodium calcium aluminum magnesium silicate hydroxide (Na, Ca)0.33(Al, Mg)2 (Si4O10) (OH)2nH2O Because montmorillonite clay is hydrophilic, it is not compatible with most polymers and must be chemically modified to make its surface more hydrophobic [10] The guar gum particles can go throw the larger particles and block the flow through them [1] Previous studies have shown that the guar gum reduced friction between steel and paraffin as the base fluid The use of guar gum has attracted great interest in the polymer industry during the past decade as polymer modified clay exhibited much better mechanical properties when compared with the virgin polymer or conventional micro and macrocomposites [11,12] Effects of the drilling mud modified with polymer on the rheological properties and fluid loss of drilling muds have been documented in the literature by several researchers are summarized in Table Mathematical modeling studied concerning the well and pipeline flow of thixotropic drilling muds and crude oils Drilling muds (oil-based muds, water-based muds) exhibit complex rheological behavior (Bingham or Herschel-Bulkley model) The limitations of the mathematical modeling studies concerning thixotropic drilling mud and crude oil flows have two main causes Despite recent advancements in tools such as quality HTHP/LT (high-tempera ture/high-pressure/low- temperature) viscometers, a unified rheological model valid for a wide range of pressures, temperatures, and flow regimes which could account for complex rheological effects such as thixotropic and yield stress still does not exist [13,14] The role of drilling fluid is to pass through formations with high porosity while keeping all its rheological properties and without causing damage to the crossed formations To reduce the mud toxicity, the water-based mud was developed The studies carried out used a drilling fluid containing water, a natural or synthetic polymer, and additives The polymers currently used in the oil industry are cellulosic, guar gum, xanthan gum, polyacrylates, polyacrylamides and maleic anhydride derivatives Control of drilling fluid properties is essential when encountering unconsolidated formations in complex geometries These properties include fluid density, rheological parameters (viscosity and yield stress) [15] In this study, enhancing the sensing and rheological properties of bentonite drilling mud modified with guar gum at different temperatures were tested and quantified with the electrical resistivity of the drilling mud Objectives The overall objective was to quantify the effect of temperature on the electrical resistivity and rheological properties of bentonite drilling mud modified with guar gum The specific objectives are as follows: (i) Evaluate the effect of guar gum on the electrical resistivity (nondestructive and sensing properties) and rheological properties of the bentonite drilling muds at different temperatures (ii) Investigate the relationship between the electrical resistivity of the drilling mud and the rheological properties of the bentonite drilling mud so that it can be used as a real- time monitoring parameter Materials and methods 3.1 Guar gum Commercially available guar gum, purity of 100% was used for this study, the appearance of yellowish-white, pH varied between 5.5 to 6.2 (1% solution) and density at 25 °C was 0.8 g/cm3 3.2 Bentonite In this study, commercially available bentonite was used The chemical composition of the bentonite has been identified using X-ray diffraction as shown in Fig Table Literature review on applications of polymer in drilling operations References Polymer type % of polymer (by dry weight) Applications Temperature (°C) Tests Remarks [2] soda ash, Carboxi Methyl Cellulose (CMC) and Drispac polymer Starch and xanthan gum Xanthan gum and the scleroglucan Up to 1.5% Water based drilling mud 25 °C ± °C Rheological properties (PV, YP, AV and Gel strength) The rheological properties of drilling muds significantly improved Up to 10% drilling fluid 95 °C Fluid loos and filter cake Up to 20% Oil and water based drilling mud Water based drilling mud Water based drilling mud Hydraulic fracturing 25 °C ± °C Shear stress-shear strain rate, flow index, n and consistency, k Increased the stability of the borehole Rheological properties of drilling muds increased 70 °C Rheological properties (PV, YP, AV and Gel strength) Rheological properties and shear stress-shear strain rate Permeability, and rheological properties Water based drilling mud Water based drilling mud 50 °C Different applications were used Temperature ranged between 25 °C to 95 °C [13] [15] [19] [20] [21] [22] Current Study Remarks Polyoxyalkyleneamine Xanthan gum and Starch Guar gum Up to 27% Sugarcane and polyanionic cellulose Guar gum Up to 0.2% Different polymer types were used Up to 27% of polymer was used Up to 2% up to 2% Up to 1% 25 °C ± °C 85 °C 25 °C–85 °C Shear stress-shear strain rate, and rheological properties (PV, YP, AV) Electrical resistivity and rheological properties Rheological properties is the popular test to characterize the effect of polymer Enhanced the rheological properties of drilling mud The rheological properties of drilling muds improved Permeability decreased and the rheological properties increased Enhanced the rheological properties of drilling mud Electrical resistivity correlated well with rheological properties No electrical resistivity properties has been studied Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 50 50 60 strength 10 (Gel 100 ) of the drilling mud were measured In this study, the bentonite content in drilling mud was varied up to 8% by the weight of water Bentonite drilling mud modified with varying amount of guar gum up to 1% by total weight of drilling mud were tested in the temperature range of 25 °C to 85 °C using a viscometer with the speed range of 0.3 to 600 rpm In this study, 150 tests were conducted to evaluate the effect of guar gum on sensing and rheological properties of drilling mud Beidellite (Na,Ca0.5)0.3Al2((Si,Al)4O10)(OH)2 · nH2O 100 MT 150 Beidellite (Na,Ca0.5)0.3Al2((Si,Al)4O10)(OH)2 · nH2O 200 Quartz (SiO2) 250 MT 300 Quartz (SiO2) NaAlSi3O8 – MT* Intensity (Counts) 350 Kaolinite (Al2Si2O5 (OH)4) Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) 400 Kaolinite (Al2Si2O5 (OH)4) MT 450 Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx Modeling 4.1 Bingham plastic model 0 10 20 30 40 70 80 90 100 2-Theta (o) * MT: Montmorillonite (Na, Ca) 0.33(Al, Mg) 2(Si4O10) (OH) 2·nH2O Fig XRD pattern for bentonite clay 3.3 XRD characterization An X-ray diffraction (XRD) analysis was performed in order to determine the chemical composition of bentonite at 25 °C The XRD pattern of the particles was obtained using the Siemens D5000 powder X-ray diffraction device XRD analyses were performed on bentonite passing sieve No 200 (75 lm) The powder (2 g) was placed in an acrylic sample holder (3 mm) depth The sample was analyzed by using parallel beam optics with CuKa radiation at 40 kV and 30 mA The sample was scanned for reflections (2h) from 0° to 90° in steps of 0.02° and s count time per step 3.4 Thermogravimetric analysis (TGA) Thermogravimetric analyses curves, mass loss (TGA) and rate of mass loss (derivative with respect to temperature) (DTG) were quantified using a Setaram TGA 500 apparatus at a heating rate of 10 °C/min for a mass sample of about 20 mg The sample was loaded in a platinum pan (¾ full) This was followed by the introduction of N2 gas into the TGA compartment for to purge the likely oxygen in the environment of the system After the purging, the sample was heated in the N2 atmosphere from room temperature to the maximum of 800 °C The weight loss percentage and temperature relationships were obtained for the samples In this study, the TGA and DTG curves were obtained for bentonite, guar gum and bentonite modified with 1% of guar gum The Bingham plastic model was the first two-parameter model that gained widespread acceptance in the drilling industry and is represented as follows: s ẳ YP ỵ PV c_ ð1Þ where s: shear stress (Pa); YP: yield point (Pa); PV: plastic viscosity (cP) and c_ : shear strain rate (s1) 4.2 Nonlinear model parameters (NLM) The electrical resistivity (q) of drilling mud using bentonite (B), guar gum (GG) was influenced by the composition of the drilling muds and temperature (T (°C)) It is being proposed to relate the model parameters to the independent variables (bentonite content and guar gum content) using a nonlinear power relationship Hence the effects of bentonite and guar gum on the electrical resistivity of the drilling muds were separated as follows: q ¼ a Bịb Tịc ỵ d Bịe Tị f ðGGÞ g ð2aÞ Based on 64 data from the current study and using nonlinear optimization following relationship was obtained: q¼ 33:6 T 0:3 B 0:5 3:5 GG0:9 B0:4 T 0:07 Forð25 C T 85 CÞ ð2bÞ The NLM parameters were obtained from multiple regression analyses using the least square method The relation between experimental and predicted data of the electrical resistivity (q) of drilling mud using Eq (2b) shown in Fig and the coefficient of determination for the 64 data was 0.93 4.3 Correlation between rheological properties and electrical resistivity 3.5 Electrical resistivity of drilling mud In this study, two different resistivity devices were used to measure the electrical resistivity of drilling mud A digital resistivity meter was used to measure the electrical resistivity of fluids, slurries, and semi-solids with resistivities in the range of 0.01 X-m to 400 X-m Also, a conductivity meter with conductivity (inverse of resistivity) in the range of to 199.9 lS/cm was also used to compare the results The electrical resistivity of the modified drilling mud with guar gum was measured using the resistivity meter and conductivity meter at various temperatures Both of the devices were calibrated using standard sodium chloride (NaCl) solution Changes in rheological properties with temperature for the bentonite drilling mud modified with guar gum can be related to the electrical resistivity as follows: YP or PV or AV or Gel100 or Gel1000 ẳ h qịL ỵ M ðqÞN ð3Þ where YP: yield stress (Pa); PV: plastic viscosity (cP); AV: apparent Viscosity (cP); Gel1000 : gel strength at 10 s (Ib/100ft2); Gel100 : gel strength at 10 (Ib/100ft2); q: electrical resistivity of drilling mud using Eq (2) and h, L, M and N are model parameters and are summarized in Table 4.4 Hyperbolic model 3.6 Rheological properties The rheological properties yield point (YP), plastic viscosity (PV), apparent viscosity (AV), gel strength 10 s (Gel 1000 ) and gel The hyperbolic relationship to represent the variation of the compressive strength with curing time for cemented sand [16] The hyperbolic relationship to predict the maximum shear stress Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx 120 Weigth (%) 100 α tensile strength of sulfate contaminated CL soils with and without polymer treatment [18] Based on the inspection of the test data following relationship is proposed: -a- ε 80 Bentonite 60 Y ¼ Yo Guar Gum (GG) Bentonite+1% GG 20 100 200 300 400 500 600 700 800 900 Temperature (oC ) 4.5 Comparison of model predictions 1.6 Derivave Weight (%/oC) Bentonite -b- 1.4 In order to determine the accuracy of the model predictions with the experimental data, both coefficient of determination (R2) and the root mean square error (RMSE) in curve fitting as defined in Eqs (5) and (6) were quantified as follows: Guar Gum (GG) 1.2 Bentonite+1% GG 0.8 12 ðx x Þðy y Þ i i B C i ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi qX ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiA R2 ¼ @qX 2 ðx x Þ ðy y Þ i i i i 0.6 0.4 0.2 -0.2 100 200 300 400 500 600 700 800 900 Temperature (oC ) Fig Thermogravimetric analysis (TGA) result on bentonite clay, guar gum and a mixture (a) TGA and (b) DTG 10 Electrical Resisvity, Measured, ρ (Ω-m) ð4Þ where Y: rheological properties of modified drilling mud with guar gum at different temperature ranging between 25 °C to 85 °C q: electrical resistivity of modified drilling mud (Eq (2)) Yo, A and B: model parameters are summarized in Table (units are based on the predicting rheological property) 40 q AỵBq X 5ị s Pn iẳ1 yi xi ị RMSE ẳ N 6ị where yi = experimental value; xi = predicted value by the model; =mean of the experimental values; y x= mean of the predicted values and N is the number of data points Results and analysis No of Data=64 R2=0.93 5.1 XRD The bentonite clay had montmorillonite (MT) (hydrated sodium calcium aluminum magnesium silicate hydroxide (Na,Ca)0.33(Al, Mg)2(Si4O10)(OH)2nH2O) (2h peaks at 7.51°, 28.12°, 35.10°, and 60.01°), kaolinite (Al2Si2O5(OH4)) (2h peak at 11.89° and 42.12°), feldspar (Albite) (NaAlSi3O8) (2h peaks at 14.32°, 29.40° and 30.01°), beidellite (Na, Ca0.5)0.3Al((Si, Al)4O10)(OH)2nH2O (2h peak at 62.05° and 73.88o) and quartz (SiO2) (2h peaks at 20.04° and 50.10°) as shown in Fig 1, similar to the chemical compositions observed by [4–17] 0 10 Electrical Resisvity, Predicted, ρ (Ω-m) 5.2 TGA analysis Fig Relation between measured and predicted electrical resistivity of bentonite drilling mud modified with guar gum limit for the bentonite drilling mud modified with acrylamide polymer and iron oxide nanomaterials [4–9] The hyperbolic relationship to predict the relation between the compressive and The thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) results were obtained for bentonite, guar gum and bentonite modified with 1% guar gum Dehydration of bentonite and guar gum was carried out in three stages as shown in Fig 2; below 120 °C, free water (interlamellar water not linked to the exchangeable cation and water between clay particles); Table TGA results for bentonite and guar gum Type of sample Bentonite clay Guar gum (GG %) Bentonite + 1% GG Temperature Range Weight loss (%) (25–120) °C (120–400) °C (400–600) °C (600–800) °C Total (%) 6.4 4.6 0.33 1.26 79.7 0.46 1.6 6.5 0.27 3.7 5.5 0.10 12.96 96.3 0.70 Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx Table Rheological and resistivity model parameters for the bentonite drilling mud with guar gum Rheological properties (Y) Nonlinear model (NLM) (Eq (3)) Yield point (YP), Pa Plastic viscosity (PV), cP Apparent viscosity (AV), cP Gel 1000 (Ib/100ft2) Gel 100 (Ib/100ft2) * Hyperbolic model (Eq (4)) h L M N R 0.1 0.2 0.0 12.2 12.7 0.06 0.1 0.0 0.0 0.0 80.8 78.4 130.6 80.5 105.7 1.4 1.3 1.2 1.2 1.4 0.81 0.81 0.82 0.80 0.80 * No of data (N) RMSE Yo A B R 3.42 3.65 8.42 4.21 7.31 67.6 793.6 937.6 107.3 187.6 0.03 0.0002 0.0002 0.015 0.004 0.011 0.001 0.001 0.008 0.005 0.82 0.82 0.84 0.80 0.80 RMSE 4.36 5.25 9.17 3.40 4.95 44 51 49 42 46 Units: X-m/predicting rheological property between 120 °C and 400 °C, water linked to the exchangeable cation of the smectite interlamellar space; The weight loss between 400 °C and 600 °C is due to the dehydration of the clay minerals such as aluminum silicate and between 600 °C and 800 °C the dehydration of calcium silicate as shown in Fig The heating rate used in these tests was 10 °C/min which does not allow equilibrium of weight loss at 105 °C (standard temperature for determining free water), as shown in Fig 2(b) Total weight loss for bentonite between 25 °C to 120 °C was 6.4% and for guar gum was 4.6% and it decreased to 0.33% when the bentonite modified with 1% guar gum as summarized in Table The guar gum treatment strongly modified the free water dehydration (25–120 °C) When the temperature changed from 120 °C to 400 °C, the weight loss increased to 1.26% and 79.7% for bentonite and guar gum respectively For temperature range between 400 °C to 600 °C, the total weight loss for bentonite was 1.6% and for guar gum was 6.5% as summarized in Table When the temperature changed from 600 °C to 800 °C, the weight loss increased to 3.7% for bentonite and decreased to 0.1% when the bentonite modified with 1% of guar gum as summarized in Table Additional of 1% of guar gum (by dry weight) to the bentonite decreased the total weight loss at 800 °C for bentonite clay from 13% to 0.7%, about a 95% reduction as summarized in Table That is also indicative of guar gum interacting with the bentonite particles resistivity by about 59% as shown in Fig This is a clear indication of the sensitivity of electrical resistivity to the bentonite content and was represented as follows: 5.3 Electrical resistivity a ¼ 0:5 Bị0:5 ỵ 0:01 Bị1:5 GGị0:7 Increasing the bentonite content (B) and guar gum content (GG %) in the drilling mud nonlinearly decreased the electrical resistivity Increasing the bentonite content from to 1% reduced the electrical resistivity of drilling mud from 19.5 X-m to 10.4 X-m, a 46% reduction as shown in Fig The electrical resistivity decreased from X-m to 3.3 X-m when bentonite content was increased from 2% to 8% at 25 °C as shown in Fig Increasing bentonite content from 2% to 8% (by weight of water) reduced the electrical Electrical Resisvity, ρ (Ω-m) Expermintal Data Model (Eqn.7) 15 ρ = 19.5 − B%ị 0:06 ỵ 0:056 B%ị R2 ẳ 0:99; No: of data ẳ 10 7ị With increasing the temperature from 25 °C to 85 °C the electrical resistivity of drilling mud with 6% of bentonite clay decreased by 24% as shown in Fig 5(b) Additional of 1% of guar gum to drilling mud with 6% of bentonite the electrical resistivity (q) decreased by 28% at room temperature as shown in Fig 5(b) With increasing of bentonite, guar gum and temperature the electrical resistivities of drilling mud nonlinearly decreased as shown in Fig Another nonlinear relationship (Eq (9)) was used to predict the electrical resistivity (q) with increasing the guar gum and temperature of bentonite drilling mud (Fig 5) Model parameters were correlated with bentonite and guar gum content as shown in Eqs (9) and (10) q ẳ bTịa 8ị b ẳ 50 Bị0:9 ỵ 1:1 Bị0:7 GGị0:5 No: of Data ẳ 15; R2 ẳ 0:93 No: of Data ẳ 14; R2 ẳ 0:82 9ị 10ị where q: electrical resistivity of modified drilling mud at different temperatures (25 °C T 85 °C) q : electrical resistivity of modified drilling mud at T = 25 °C b and a are model parameters Rheological properties Rheology of the drilling mud formulated with different percentages of bentonite (B) up to 8%, and varying the amount of guar gum (GG) up to 1% at different temperatures were studied Yield point (YP), plastic viscosity (PV), apparent viscosities (AV), and gel strengths (Gel) were measured according to API specifications YP and PV were determined based on Bingham plastic model Rheology properties of the drilling muds are summarized as follows: 25 20 q ¼ 19:5 B(%) 0.06 + 0.056 ∗ (B%) Type equation here 10 6.1 Yield point (YP) 0 Bentonite Clay, B (%) Fig Effect of bentonite clay on the electrical resistivity of water based drilling mud Additional of bentonite and guar gum increased the yield point (YP) of the drilling mud YP of drilling mud increased from Pa to 31 Pa when the bentonite content changed from 2% to 8% at 25 °C as shown in Fig Additional of 0.3% of guar gum to drilling mud with 2% and 8% bentonite increased the yield point (YP) by 25% and 28% respectively at room temperature The YP of drilling mud with 2% and 8% bentonite content modified with 0.3% guar gum Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx 10 GG=0% GG=0.3% GG=0.6% GG=1% Model (Eqn.8) Electrical Resisvity, ρ (Ω-m) 6.6 5.5 5.1 4.5 4.5 4.0 3.5 2.5 2.0 1.9 1.7 1.6 1.2 0.7 -a- 0.3 25 20 25 30 35 40 45 50 55 60 65 70 75 80 85 Temperature, T (oC) 65 85 18 GG=0% GG=0.3% GG=0.6% GG=1% Model (Eqn.8) 16 Yield Point, YP (Pa) -b- 5.5 45 Temperature, T (oC) 90 Electrical Resisvity,ρ (Ω-m) 4.3 4.5 3.5 14 -b14.3 14.8 GG=0% GG=0.3% GG=0.6% GG=1% 4% Bentonite 15.5 13.4 14.1 14.7 12.2 12.2 12 13.2 10.8 9.9 10.2 9.5 10 8.9 6.2 2.2 Bentonite=6% 2.5 25 45 65 85 Temperature, T (oC) 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 60 Temperature , T(oC) Yield Point, YP (Pa) Bentonite=8% 3.5 2.5 GG=0% GG=0.3% GG=0.6% GG=1% 8% Bentonite -c49.1 50 Electrical Resisvity, ρ (Ω-m) GG=0% GG=0.3% GG=0.6% GG=1% 2% Bentonite -a- Yield Point, YP (Pa) Bentonite=2% 42.2 42.0 39.6 40 38.7 36.5 35.7 33.5 31 32.6 30.2 30 26.8 26 28.6 18.6 20 12.8 10 1.5 GG=0% GG=0.3% GG=0.6% GG=1% Model (Eqn.8) 0.5 25 -c- 20 25 30 35 40 45 50 55 60 Temperature, T 65 70 75 45 65 85 Temperature, T (oC) 80 85 90 Fig Variation of yield point with temperature for the bentonite drilling muds modified with guar gum (a) 2% bentonite (b) 4% bentonite and (c) 8% bentonite (oC) Fig Variation of the electrical resistivity (measured and predicted Eq (8)) with guar gum content (GG%) and temperature for bentonite drilling muds (a) 2% bentonite (b) 6% bentonite and (c) 8% bentonite decreased by 36% and 32% respectively with increasing the temperature from 25 °C to 85 °C as shown in Fig Additional of 1% of guar gum the yield point (YP) increased from 58% to 230% based on the bentonite content in the drilling mud at a temperature of 25 °C as shown in Fig 6(c) The electrical resistivity of drilling mud decreased while the yield point (YP) increased as shown in Fig 11(a) The relationships between yield point and electrical resistivity for drilling mud based bentonite modified with guar gum at temperature varied from 25 °C to 85 °C was modeled using the NLM (Eq (3)) and hyperbolic relationship (Eq (4)) as shown in Fig 11(a) The coefficient of determination (R2) for the NLM and hyperbolic models were 0.81 and 0.82 respectively as summarized in Table The root mean squares of error (RMSE) for the NLM and hyperbolic models were 3.42 Pa and 4.36 Pa respectively as summarized in Table 6.2 Plastic viscosity (PV) The PV for the drilling muds with 2%, 4% and 8% of bentonite content without guar gum at the temperature of 25 °C were 6.7 cP, 13.6 cP, 28 cP and 47.6 cP respectively When the bentonite of drilling mud with 2% and 8% bentonite was modified using 1% guar gum (by total weight of drilling mud) at room temperature PV was increased by 78% and 45% respectively as shown in Fig Increasing the temperature from 25 °C to 85 °C for drilling mud with 8% of bentonite modified with 1% of guar gum decreased the PV from 68.9 cP to 50.1 cP, a 27% reduction as shown in Fig (c) The relationships between plastic viscosity and electrical resistivity for the drilling mud based bentonite modified with guar gum at temperature varied from 25 °C to 85 °C was modeled using the NLM (Eq (3)) and hyperbolic relationship (Eq (4)) as shown in Fig 11(b) and the coefficients of determination (R2) for the NLM and hyperbolic models were 0.81 and 0.82 respectively as summarized in Table The root mean squares of error (RMSE) were 3.65 cP and 5.23 cP for the NLM and hyperbolic relationships respectively as summarized in Table Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx 16 14 Plasc Viscosity, PV (cP) 12 -a- GG=0.3% 10 GG=0.6% GG=1% GG=0.3% 12.0 GG=0.6% 10.6 10 9.4 9.2 7.7 10.1 GG=1% 7.7 7.2 6.8 6.2 4.9 5.1 4.2 2.3 2% Bentonite 0 20 40 60 Temperature, T 80 25 100 16.6 16.0 16 17.1 GG=0.3% 15.2 13.6 14 GG=0.6% 14.0 12.3 12.9 GG=1% 12 11.0 9.2 10 9.2 7.2 6.6 4.0 65 85 100 GG=0% 4% Bentonite Apparent Viscosity, AV (cP) 17.8 18.2 -b- 18 45 Temperature, T (oC) (oC) 20 90 -b- 80 70 60 50 40 GG=0% 30 GG=0.3% 20 GG=0.6% 10 GG=1% Temperature, T (oC) 8% Bentonite 0 20 40 80 60 80 100 Temperature, T (oC) 8% Bentonite 70 Fig Variation of apparent viscosity with temperature for the bentonite drilling muds modified with guar gum (a) 2% bentonite and (b) 8% bentonite 60 50 40 GG=0% 30 GG=0.3% 20 GG=0.6% 10 -c- GG=1% 0 20 40 60 80 100 Temperature, T (oC) Fig Variation of plastic viscosity with temperature for the bentonite drilling muds modified with guar gum (a) 2% bentonite (b) 4% bentonite and (c) 8% bentonite Gel Strength (10"), Gel10" (Ib/100 2) Plasc Viscosity, PV (cP) GG=0% 2% Bentonite -a- 12.9 12 Plasc Viscosity, PV (cP) 15.2 14 Apparent Viscosity, AV (cP) GG=0% 25 GG=0% GG=0.3% GG=0.6% GG=1% 2% Bentonite -a20.4 20 18.0 17.1 16.4 15.6 15 13.2 12.0 10.8 12.1 10.0 10 8.2 10.8 7.6 7.5 8.4 6.0 6.3 Apparent viscosity (AV) 25 45 65 85 Temperature, T (oC) 80 Gel Strength (10"), Gel10" (Ib/100 2) The apparent viscosity of control drilling mud with 2% and 8% of bentonite at room temperature were 7.7 cP and 63.1 cP respectively as shown in Fig Bentonite drilling mud modified with 1% guar gum (by total weight of drilling mud) at room temperature increased AV from 47% to 114% based on the amount of bentonite in the drilling mud and temperature Increasing the temperature from 25 °C to 85 °C for drilling mud with 8% of bentonite modified with 1% of guar gum decreased the AV from 93.4 to 66.5 cP as shown in Fig 8(b) The relationships between apparent viscosity and electrical resistivity for drilling mud based bentonite modified with guar gum at temperature varied from 25 °C to 85 °C was modeled using the NLM (Eq (3)) and hyperbolic relationship (Eq (4)) as shown in Fig 11(c) The coefficients of determination (R2) for the NLM and hyperbolic models were 0.82 and 0.84 respectively as summarized in Table The root mean squares of error (RMSE) were 8.42 cP and 9.17 cP for the NLM and hyperbolic relationships respectively as summarized in Table 70 -b- GG=0% GG=0.3% GG=0.6% GG=1% 8% Bentonite 68.6 60.4 60 52.8 50.4 48.6 46.8 50 45.6 42.3 40 40.8 37.0 30.2 30 38.4 42.0 45.6 28.0 22.0 20 10 25 45 65 85 Temperature, T (oC) Fig Variation of gel strength (10 s.) with temperature for the bentonite drilling muds modified with guar gum (a) 2% bentonite and (b) 8% bentonite Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx 40 Expermintal Data -a- 2% Bentonite 25 Yield Point, Yp (Pa) Gel Strength (10'), Gel10' (Ib/100 2) 30 20 15 GG=0% 10 GG=0.3% GG=0.6% 35 NLM (Eqn 3) 30 Hyperbolic Model (Eqn 4) 25 20 15 -a- 10 GG=1% No.of Data=44 0 20 40 60 80 100 Temperature, T (oC) Electrical Resisvity, ρ (Ω-m) 80 80 GG=0% GG=0.3% GG=0.6% GG=1% 8% Bentonite -b- 76.3 70.9 70 66.5 62.3 62.5 64.8 60.0 60 55.0 50.4 50 42.0 40 49.6 38.5 45.6 34.0 43.2 31.0 30 20 Expermintal Data NLM (Eqn.3) Hyperbolic Model (Eqn.4) 70 Plasc Viscosity, PV (cP) Gel Strength (10'), Gel10' (Ib/100 2) 90 60 50 40 -b- 30 20 10 10 0 No.of Data=51 Temperature, T (oC) Fig 10 Variation of gel strength (10 min) with temperature for the bentonite drilling muds modified with guar gum (a) 2% bentonite and (b) 8% bentonite 6.4.2 Gel strength 10 (Gel100 ) The Gel100 of drilling mud with 2% up to 8% of bentonite without guar gum at room temperature varied from 16 lb/100ft2 to 42 lb/100ft2 Adding 1% of guar gum to the 8% bentonite drilling mud at room temperature increased the Gel1000 by 82% Increasing the temperature to 85 °C reduced the Gel100 of the drilling mud and with 8% of the drilling mud, the reduction was 21% as shown in Fig 10(b) The relationships between Gel100 and electrical resistivity for drilling mud based bentonite modified with guar gum in the temperature range of 25 °C to 85 °C was modeled using the NLM (Eq (3)) and hyperbolic relationship (Eq (4)) as shown in Fig 12(b) The coefficient of determination (R2) was 0.80 for both NLM and hyperbolic relationships as summarized in Table The root mean squares of error (RMSE) for the NLM and hyperbolic relationships were 7.31 lb/100ft2 and 4.95 lb/100ft2 respectively as summarized in Table Apperant Viscosity, AV, (cP) 6.4.1 Gel strength 10 s (Gel1000 ) The Gel1000 of drilling mud at room temperature varied from 10 to 37 lb/100ft2 based on the bentonite clay content in the drilling mud Increasing the temperature to 85 °C reduced the Gel1000 of the 8% bentonite drilling mud modified with 1% of guar gum by 34% as shown in Fig 9(b) The relationship between Gel1000 and electrical resistivity for drilling mud based bentonite modified with guar gum in the temperature range of 25 °C to 85 °C was modeled using the NLM (Eq (3)) and hyperbolic model (Eq (4)) as shown in Fig 12(a) The coefficient of determination (R2) was 0.80 for both relationships as summarized in Table The root mean squares of error (RMSE) were 4.21 lb/100ft2 and 3.40 lb/100ft2 for the NLM and hyperbolic relationships respectively as summarized in Table 10 100 Expermintal Data 90 6.4 Gel strength (Gel) Electrical Resisvity, ρ (Ω-m) NLM (Eqn 3) 80 Hyperbolic Model (Eqn.4) 70 No.of Data=48 60 50 40 30 20 -c- 10 0 10 Electrical Resisvity, ρ (Ω-m) Fig 11 Relationship between the electrical resistivity and rheological properties of bentonite drilling mud modified with guar gum (a) yield point (b) plastic viscosity and (c) apparent viscosity Conclusions In this study, rheological properties of guar gum modified bentonite based drilling muds were related to the electrical resistivity, the sensing property identified for real-time monitoring the smart drilling muds during construction Based on the experimental study and analytical modeling following conclusions are advanced: The electrical resistivity of the drilling mud decreased with increasing bentonite content, guar gum content and temperature and it was a good sensing parameter for real-time monitoring during construction for quality control of the drilling mud and also to predict the rheological properties of drilling mud in the field Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer, Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2017.01.002 A.S Mohammed / Egyptian Journal of Petroleum xxx (2017) xxx–xxx Electrical resistivity was directly related to rheological properties of the bentonite drilling mud using the nonlinear power and hyperbolic relationships Gel Strength (10"), Gel10" (Ib/100 2) 70 Expermintal Data 60 NLM (Eqn 3) Hyperbolic Model (Eqn.4) 50 Acknowledgement -a- 40 The author would like to thanks, Dr Cumaraswamy Vipulanandan Director of the Center for Innovative Grouting Materials and Technology (CIGMAT) at the University of Houston, Houston, Texas for the help during the study work 30 20 10 No.of Data=37 References 0 10 Electrical Resisvity, ρ (Ω-m) Gel Strength (10'), Gel10' (Ib/1002) 80 Expermintal Data 70 NLM (Eqn 3) 60 Hyperbolic Model (Eqn.4) No.of Data=37 50 40 30 20 10 -b- 0 10 Electrical Resisvity, ρ (Ω-m) Fig 12 Relationship between the electrical resistivity and gel strength of bentonite drilling mud modified with guar gum (a) gel strength (10 s) and (b) gel strength (10 min) Yield point (YP) of drilling mud increased with increasing of bentonite and guar gum contents Increasing the bentonite content in the drilling mud from 2% to 8% increased the yield stress from Pa to 31 Pa Additional of 1% guar gum increased the YP up to 70% based on the bentonite clay content and temperature Plastic viscosity (PV) of drilling mud increased from 6.7 cP to 47.6 cP when the bentonite content increased from 2% to 8% at room temperature The PV increased by 45% to 80% based on the bentonite clay content and the temperature of the drilling mud Apparent viscosity (AV) of drilling mud increased from 7.7 cP to 63.1 cP when the bentonite content increased from 2% to 8% at room temperature The AV increased by 40% to 95% based on the bentonite content and the temperature of the drilling mud Using a nonlinear relationship the model parameters were related to the composition of the drilling mud Nonlinear model was effective in identifying contribution of each 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properties of drilling muds improved Permeability decreased and the rheological properties increased Enhanced the rheological properties of drilling. .. the electrical resistivity of drilling mud with 6% of bentonite clay decreased by 24% as shown in Fig 5(b) Additional of 1% of guar gum to drilling mud with 6% of bentonite the electrical resistivity. .. bentonite drilling muds modified with guar gum (a) 2% bentonite and (b) 8% bentonite Please cite this article in press as: A.S Mohammed, Electrical resistivity and rheological properties of sensing