Well test analysis research at Imperial College http://www.jipimperial.co.uk Alain C. Gringarten Professor of Petroleum Engineering Director of the Centre for Petroleum Studies

Prerequisite: actual well test data Objectives explain complex well test behaviours provide practical methods for interpreting them assess uncertainties and limitations of the corresponding analysis results as a function of the information available Prerequisite: actual well test data

JIP: Investigation of Alternative Methods for Testing Oil and Gas Wells to Eliminate Emissions 1999-2002: BP, Conoco, Norsk Hydro and Schlumberger Objective: evaluate options for testing exploration and appraisal wells without producing fluids to the surface closed-chamber testing harmonic testing re-injection in a different layer Outcome: Deconvolution 3 SPE publications, 3 MSc theses, 1 PhD thesis

22 SPE publications, 55 MSc theses, 10 PhD theses JIP: Well test analysis in gas condensate and volatile oil reservoirs below saturation pressure 2002-2005: Anadarko, Burlington, BHP Billinton, Britannia Operator Ltd, ConocoPhillips, GdF, RERI, Total and UK DTI 2005-2008: BG Group, Burlington, ConocoPhillips, ENI, Petro SA, Petrom and Total Objectives: explain well test behaviours below saturation pressure 22 SPE publications, 55 MSc theses, 10 PhD theses

Well test analysis in gas condensate and volatile oil reservoirs below saturation pressure Outcome: 2-phase bank develops below saturation pressure Well productivity evaluation requires capillary number effect 2 or 3-region composite well test behaviour with 1-phase pseudo-pressures for gas condensates or pressures for volatile oil Homogeneous behaviour with 2-phase pseudo pressure In sandstone reservoirs, reservoir effective k = arithmetic average core k Correct 2-phase bank total compressibility is required to estimate the bank outer radius Fracturing vertical wells or drilling horizontal wells is equally effective for improving productivity skin vs. rate is the same above and below saturation pressure with 2-phase pseudo pressures below saturation pressure.

CDFi (pdew= 3040 psia) Wellbore skin effect Gas rate, MMscf/D 12 10 8 6 4 2 Q Above pdew Below pdew 2-j m(p) FP18 FP20 FP36 FP30 1-j m(p) S = -0.9 Q + 12.80 FP36 Wellbore skin effect FP30 FP18 FP20 S = 0.3 Q + 0.05 FP13 S = 0.3 Q + 0.05 FP3 FP5 1 3 5 7 9 11 13 Gas rate, MMscf/D

JIP: Well Test Analysis in Complex Systems Complex Fluids, Complex reservoirs, and Complex Wells 2009-2013: BG Group, BHP Billiton, Eon-Rurhgas, Petro SA and Schlumberger Gas condensate and volatile oil below saturation pressure Shale gas: Molecular Modelling Macro-scale experimental studies Darcy scale modelling Well test analysis Geologically complex reservoir geometries Semi-infinite channels with non-parallel boundaries Meandering channels Pinch-out boundaries 9 SPE publications, 26 MSc theses

Well Test Analysis in Complex Systems Complex Fluids, Complex reservoirs, and Complex Wells Shale gas outcome: Stable storage of methane is impossible in the kerogen itself High CH4 molecule concentrations are trapped by K+ ions on illite faces in kerogen-illite or illite-illite interfaces with apertures h lower than or equal to 8 Å Two partial storage sites exist in larger interfaces h ≥ 10 Å, due to irreversible anti-adhesion processes The density of the stored gas in illite-illite interfaces is very high compared to pressured free gas (up to several thousands of CH4 moles per cubic meter of interface). The total gas-in-place can be evaluated by measuring the distribution and size of mineral interfaces. The amount and rate of gas that can be extracted depends on the ability of enlarging clay mineral interfaces at depth (for instance by hydraulic fracturing).

INTERSECTING BOUNDARIES 105 104 103 102 10 80o 31o Wedge 2 d1 = 32 m d2 = 30 m a = 31o Wedge 1 d1 = 13 m d2 = 27 m a = 80o nm(p) Change and Derivative (kPa) 10-4 10-3 10-2 10-1 1 10 102 103 Elapsed time (hrs)

nm(p) Change and Derivative (kPa) MEANDERING CHANNEL Elapsed time (hrs) 10-4 10-3 10-2 10-1 1 10 102 103 nm(p) Change and Derivative (kPa) 104 103 102 10 1 80o Channel d1 + d2 = 15 m Wedge d1 = 7 m d2 = 4 m a = 84o

11 SPE publications, 19 MSc theses JIP: Deconvolution 2005-2008: BG Group, BHP Billiton, BP, Chevron, ConocoPhillips, ENI, GdF, Occidental, Petro SA, Saudi Aramco, Schlumberger, Shell, Total and Weatherford 2009-2013: Anadarko, BG Group, Chevron, ConocoPhillips, Inpex, Petro SA, Saudi Aramco, Schlumberger, Shell, and Total Objectives: assess the uncertainty in the well test interpretation model through deconvolution extend deconvolution to multiple interfering wells Outcome: Monte-Carlo Deconvolution 11 SPE publications, 19 MSc theses

Deconvolution 3800 4000 4200 4400 4600 4800 5000 5200 5400 -10 10 20 30 40 50 60 70 80 90 100 110 120 130 Pressure (psia) Elapsed time (hrs) -20 140 Gas Rate (MMscf/D) 3800 4000 4200 4400 4600 4800 5000 5200 5400 -10 10 20 30 40 50 60 70 80 90 100 110 120 130 Pressure (psia) Elapsed time (hrs) -20 140 Gas Rate (MMscf/D) 12

Deconvolution: boundary identification Test 1 (Exploration) FP06 Test 2 (Production) FP35 Maureen A2 13

Deconvolution: boundary identification 100 FP 06 (Exploration build-up) FP 35 (Production build-up) 10 1 Test duration 0.1 Derivative, psia 0.01 Maximum flow period durations 0.001 Build-ups during exploration and production tests in Maureen well A2. Boundaries are not visible, whereas there are in the deconvolved derivative of the production test build-up. The deconvolved derivative confirms the analysis model. 0.0001 0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 100000 1E+06 1E+07 1E+08 Time, hrs 14

Deconvolution: boundary identification 100 Dimensionless unit rate pressure & derivative type curves FP 06 (Exploration build-up) FP 35 (Production build-up) 10 lambda = 1.e+05 lambda = 5e+05 lambda = 8e+05 lambda = 1.0e+06 Deconvolved derivative for various smoothness values 1 Test duration 0.1 Derivative, psia 0.01 Maximum flow period durations 0.001 Build-ups during exploration and production tests in Maureen well A2. Boundaries are not visible, whereas there are in the deconvolved derivative of the production test build-up. The deconvolved derivative confirms the analysis model. 0.0001 Knowledge gap 0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 100000 1E+06 1E+07 1E+08 Time, hrs 15

Monte Carlo deconvolution

The Atlantic Refining Co…) JIP: New developments in well test analysis SPE papers with WT 50 100 150 200 250 300 350 Year 1947 1949 1951 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 Number of publications Horizontal wells Electronic gauges Permanent Hardware/Completion MHF IKVF Stehfest Green’s functions Deconvolution Laplace transform Mathematical tools Horner Derivatives Methodology Type Curve Analysis MDH MBH Commercial Software Interpretation methods IOC Shell, Gulf Oil Corp, The Atlantic Refining Co…) UNIVERSITIES Texas A&M, Stanford SERVICE Flopetrol Schlumberger NICHES ??????? DEVELOPERS

Value tied to power in Identification and Verification New developments in well test analysis Value tied to power in Identification and Verification Poor None ANALYSIS METHOD IDENTIFICATION VERIFICATION 50’s Straight lines Fair ( limited) Fair to Good 70’s Pressure Type Curves Very Good 80’s Pressure Derivative Much better 00’s Deconvolution Same as derivative Next ? >>> >>> 41

New developments in well test analysis 2014-2017 Multiwell deconvolution Shale oil and gas Molecular Modelling Macro-scale experimental studies Darcy scale modelling Well test analysis

New developments in well test analysis Multiwell deconvolution

New developments in well test analysis Shale oil and gas

New developments in well test analysis Shale oil and gas

New developments in well test analysis Shale oil and gas Fracture Matrix