PowerPoint Presentation Understanding DST procedure Interpreting DST pressure charts Dong Lee 30 Jul 2016 We shall discuss about The DST concept Surface Well Test Components Test Sequence of DST Dat.
Understanding DST procedure & Interpreting DST pressure charts Dong Lee 30 Jul 2016 We shall discuss about: The DST concept Surface Well Test Components Test Sequence of DST Data Obtain from DST Interpreting DST pressure chart Well Test in Practice 1- DST Concept Objectives are to understand: • • • • The The The The DST concept main DST components main DST pressures main DST types Drill-stem testing (DST) is a type of temporary completion that is used to evaluate the formation and inspect a reservoir’s properties The measurement of the reservoir properties by the DST can be delivered directly or indirectly Direct measurements means that the data are recorded when the tool assembly was down in the hole: - Initial Reservoir Pressure (Pi) - Flow rate measurement (Q) - Obtaining a recovery sample of the formation fluids (PVT) Indirect measurement or empirical measurements are those parameters that yield from the use of equations and it includes: - Productivity index (PI) - Effective permeability of the formation to the fluid flow (k) - Formation transmissibility (kh/μ) - Skin factor (s) - Drainage radius of the investigation test - and detection of reservoir anomalies (such as barriers, fluid contacts, permeability changes or layered zones) The main DST component The basic equipment for a drill stem test consits of a string (tubing or drillpipe), a packer and a valve The string channels the flow to surface The packer is a rubber element to isolate the zone to be tested The tester valve provides a method of controlling the well near the reservoir The main DST pressures Ph: Hydrostatic pressure Pf: Formation pressure Pc: Cushion pressure Generally, the relationship among these pressures is: Ph > Pf > Pc Basic DST Tools The Packer isolates the formation from the annulus, the two pressures (Ph and Pf) must be isolated from one another The Tester valve controls the formation - shut the well downhole to minimize wellbore storage effect - isolates annular fluid from cushion while RIH, preventing U-tubing -provides a seal for pressure test the string After the packer is set and sealed, the test valve can then be opened and hydrocarbons can be produced to surface This will only occur if Pc < Ph The DST Types Basic DST Operation • During the initial phase of the test, the wellbore fluids, and, later, the drilling fluid (mud) that has invaded the formation in the vicinity of the wellbore flow to surface This is known as the cleanup period Cleanup is complete when the well effluent at surface is reservoir fluid that contains no mud particles or cuttings at surface (BSW Pf > Pc Basic DST Tools The Packer