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ADVANCED WELL STIMULATION STRATEGIES Leo Roodhart (Roodhart Energy Consultancy)6 Well Stimulation Advisor Gerrit Nitters (Nitters Petroleum Consultancy Int.)6 Well Stimulation Advisor HSE ! Exit ! Drills ! Etc. Introduc:on Objectives • Identify the method to enhance and optimize the inflow performance • Select candidates for hydraulic fracturing treatments, • Understand the design and execution of and how to • Evaluate pre‐treatment minifrac/data frac treatments • Understand the design and execution of and • Evaluate hydraulic fracturing treatments • Understand and work with state of the art hydraulic fracturing simulators • Understand the environmental impact of fluids used in production enhancement treatments Par∃cipants Introduc∃on Cases you would like to present Agenda ! Day 1 ! ! ! ! Introduc:on and development op:ons Inflow performance Basics of forma:on damage and remedia:on Chemistry of Matrix acidising (sandstones and Carbonates) and addi:ves ! Day 2 ! ! ! Acidising placement and diversion techniques Opera:onal aspects, Quality Control and HSE Carbonate acid fracturing (if appropriate) ! Day 3 ! ! ! Hydraulic Fracturing: op:ons and candidates selec:on Fracturing Fluids and Proppants Fracturing design ! Day 4 ! ! ! ! Execu:on procedures and minifrac/DFIT analysis Solving near well bore restric:ons Real :me fracturing treatment analysis Hydraulic Fracturing logis:cs and execu:on ‐ HSE ! Day 5 ! ! ! ! Mul:ple fractures: design and control Fracture mapping Summary Group exercise: hydraulic fracturing design by hand Par:cipant Cases Some Development op:ons Well Path ! Vertical well (open hole, cased and perforated etc.) ! Horizontal hole (bare foot, slotted liner, C&P) ! Multi‐Laterals ! (Multiple) Fractured vertical well ! (Multiple) Fractured Horizontal well ! Fractured Multi‐Laterals ! Snake well ! Cork screw well Reservoir Characterisa:on ! Thick and homogeneous, no gas‐cap, no aquifer ! Thick and homogeneous with gas‐cap and aquifer ! Layered ! Laminated ! Naturally Fractured ! Naturally Fractured under Waterflood ! Compartmentalized Reservoir Composi:on ! Sandstones ! High permeability ! Low permeability ! Carbonates ! Limestones ! Dolomites ! Shales ! Extremely low permeability ! Coal ! Coal bed methane ! Geothermal Well path Reservoir Characterization Vertical well hydrofracced well slanted well kv/kh < 0.1 horizontal well Fractured horizontal well kv/kh > 0.1 Thick and Homogeneous No gas cap or aquifer Thick and Homogeneous With gas cap and aquifer Parallel horizontal wells preferred Gas water water water Layered Laminated Naturally fractured Prop Natural fractures water water water Well path Reservoir Characterization Naturally fractured Under waterflood Vertical well Plug natural fractures hydrofracced well slanted well Frac water injectors Short closely spaced parallel wells normal to fractures In water injectors Shale gas Heavy oil Acid fingering Tight carbonates Propped fracture horizontal well Fractured horizontal well Coal Reservoir vs Conven∃onal Petroleum Traps CBM: • Laterally extensive coal seams • Gas produced in coalifica:on process and adsorbed onto coal surfaces • Limited communica:on between wells • Water usually fills pore/fracture space • Water produc:on then gas • Gas is always dry Conven:onal: ¥ Structurally trapped by seal ¥ Hydrocarbon presence due to buoyancy ¥ Gas compressed into pore space ¥ 1 well may drain en:re trap Hydraulic fracturing in CBM ! The main objec:ve is to connect up with and enlarge an already exis:ng fracture network ! Process similar to that used in conven:onal gas wells ! The hydraulic fracture may extend from the target forma:on into a USDW* ! The fracture may connect through natural fracture systems to permeable forma:ons, poten:ally entering a USDW* ! Fracture behavior through coal and other geological strata depends on site‐specific factors such as the following: ! Physical proper:es, types, thicknesses, and depths of the coalbeds and the surrounding forma:ons ! Presence of exis:ng natural fracture systems and their orienta:on in the coalbeds and surrounding forma:ons ! Amount and distribu:on of stress (i.e., in‐situ stress), and the stress contrasts between the targeted coalbeds and surrounding forma:ons ! Hydraulic fracture s:mula:on design *Underground Source of Drinking Water CBM: Fraccing or horizontal? Fracture s∃mula∃on ! Fracture s:mula:on significantly increases costs (may need re‐ fraccing?) ! Needs competent coals (soχ coal fracs won’t stay open) and ! Isola:on from aquifers Horizontal Wells ! Much higher costs ! good for lower permeability coals or where land access is an issue ! Boreholes can become blocked with fines and/or borehole collapse increasing costs for clean out Natural fracture systems ! Hydraulic fractures link into the exis:ng fracture network system ! fracturing fluids can move beyond the propped sec:on of hydraulically induced fractures ! 200 to 600 feet beyond the propped por:ons of induced or enlarged fractures. ! Steidl 1993; Diamond 1987a and b; Diamond and Oyler, 1987 σH Gunnedah Basin Bohena Seam Horizontal wells vs fracturing ! Face cleats are well developed & preferen:ally oriented normal to the prevailing tensional stress regime ! No buη cleats Source: Eastern Star Gas Produc:vity enhancement techniques Chemical Methods Ð Remove (formation) damage ¥ Matrix acidising ¥ Acid washes ¥ Chemical flushes with surfactants, solvents, mutual solvents, etc ¥ Microbial stimulation Mechanical Methods Ð Improve inflow area ¥ Hydraulic fracturing Ð from frac&packs to massive hydraulic fracturing ¥ Explosive fracturing including the use of propellants, "Radialfrac" ¥ Underreaming ¥ Re- and additional perforating Combined Mechanical/Chemical Methods ¥ Acid-fracturing including propped acid fracturing, ¥ Closed Fracture Acidising (CFA) Thermal Methods Ð Heavy oil ¥ Steam soak ¥ In-situ heat generation ¥ Electrical heating 17 Produc:vity enhancement techniques Chemical Methods Ð Remove (formation) damage ¥ Matrix acidising ¥ Acid washes ¥ Chemical flushes with surfactants, solvents, mutual solvents, etc ¥ Microbial stimulation Mechanical Methods Ð Improve inflow area ¥ Hydraulic fracturing Ð from frac&packs to massive hydraulic fracturing ¥ Explosive fracturing including the use of propellants, "Radialfrac" ¥ Underreaming ¥ Re- and additional perforating Combined Mechanical/Chemical Methods ¥ Acid-fracturing including propped acid fracturing, ¥ Closed Fracture Acidising (CFA) Thermal Methods Ð Heavy oil ¥ Steam soak ¥ In-situ heat generation ¥ Electrical heating 18 IT’S ALL ABOUT IMPROVING THE INFLOW PERFORMANCE ALL ABOUT CONNECTIVITY! 19 ... enhancement treatments Par∃cipants Introduc∃on Cases you would like to present Agenda ! Day 1 ! ! ! ! Introduc:on and development op:ons Inflow performance Basics of forma:on damage and remedia:on ... Chemistry of Matrix acidising (sandstones and Carbonates) and addi:ves ! Day 2 ! ! ! Acidising placement and diversion techniques Opera:onal aspects, Quality Control and HSE Carbonate acid fracturing (if appropriate) ! Day 3 ! ! ! Hydraulic Fracturing: op:ons and candidates selec:on ... Hydraulic Fracturing logis:cs and execu:on ‐ HSE ! Day 5 ! ! ! ! Mul:ple fractures: design and control Fracture mapping Summary Group exercise: hydraulic fracturing design by hand Par:cipant Cases Some Development op:ons