Method for measuring formation properties with a time-limited formation test
AssigneeSchlumberger Technology Corporation
InventorsJean-Marc Follini, Julian Pop
Life of this patent
Estimating the term…
Abstract
An apparatus and method for determining at least one downhole formation property is disclosed. The apparatus includes a probe and a pretest piston positionable in fluid communication with the formation, and a series of flowlines pressure gauges, and valves configured to selectively draw into the apparatus for measurement of one of formation fluid and mud. The method includes performing a first pretest to determine an estimated formation parameter; using the first pretest to design a second pretest and generate refined formation parameters whereby formation properties may be estimated.
Claims50
A method for determining formation parameters using a downhole tool positioned in a wellbore adjacent a subterranean formation, comprising:
- performing a first pretest of the formation to determine an initial estimate of the formation parameters;
- designing pretest criteria for performing a second pretest based on the initial estimate of the formation parameters;
- performing a second pretest of the formation according to the designed criteria whereby a refined estimate of the formation parameters are determined.
A method for determining at least one formation fluid property using a formation tester, comprising:
- collecting a first set of data points representing pressures in a pretest chamber of the formation tester as a function of time during a first pretest;
- determining a set of parameters for a second pretest, the set of parameters being determined based on estimated formation properties derived from the first set of data points and a time remaining for performing the second pretest;
- performing the second pretest using the set of parameters;
- collecting a second set of data points representing pressures in the pretest chamber as a function of time during the second pretest;
- and
- determining the at least one formation fluid property from the second set of data points.
A formation tester, comprising:
- a housing having a flow line and a pretest chamber, the flow line and the pretest chamber are in fluid communication;
- a probe disposed on an exterior of the housing, the probe being in fluid communication with the flow line, and the probe being adapted to establish fluid communication with formation fluids;
- a probe isolation valve disposed in the flow line between the probe and the pretest chamber, the probe isolation valve being adapted to prevent fluid communication between the probe and the pretest chamber;
- a probe pressure gauge disposed in the flow line between the probe isolation valve and the probe, the probe pressure gauge being adapted to measure fluid pressures in the probe;
- a pretest chamber gauge disposed in the flow line between the probe isolation valve and the pretest chamber, the pretest chamber gauge being adapted to measure fluid pressures in the pretest chamber;
- a flow line isolation valve disposed in the flow line such that the pretest chamber is located between the pretest chamber gauge and the flow line isolation valve, the flow line isolation valve being adapted to prevent fluid communication between the pretest chamber and a remainder of the flow line lying beyond the flow line isolation valve;
- an equalization flow line branching off the flow line at a location between the pretest chamber and the flow line isolation valve, the equalization flow line being adapted to provide fluid communication between the flow line and the well fluids in the borehole;
- and
- an equalization valve disposed in the equalization flow line, the equalization valve being adapted to prevent the fluid communication between the flow line and the well fluids in the borehole.
A method for determining a termination condition for a drawdown operation using a formation tester in a formation penetrated by a borehole, comprising:
- setting a probe of the formation tester against a wall of the borehole so that a pretest chamber is in fluid communication with the formation, a drilling fluid in the pretest chamber having a higher pressure than the formation pressure;
- decompressing the drilling fluid in the pretest chamber by withdrawing a pretest piston at a constant drawdown rate;
- collecting data points representing fluid pressures in the pretest chamber as a function of time;
- identifying a range of consecutive data points that fit a line of pressure versus time with a fixed slope, the fixed slope being based on a compressibility of the drilling fluid, the constant drawdown rate, and a volume of the pretest chamber;
- and
- terminating the drawdown operation based on a termination criterion after the range of the consecutive data points is identified.
A method for determining an estimated formation pressure from a drawdown operation using a formation tester in a formation penetrated by a borehole, comprising:
- setting the formation tester against a wall of the borehole so that a pretest chamber of the formation tester is in fluid communication with the formation, a drilling fluid in the pretest chamber having a higher pressure than the formation pressure;
- decompressing the drilling fluid in the pretest chamber by withdrawing a pretest piston in the formation tester at a constant drawdown rate;
- collecting data points representing fluid pressures in the pretest chamber as a function of time;
- identifying a range of consecutive data points that fit a line of pressure versus time with a fixed slope, the fixed slope being based on a compressibility of the drilling fluid, the constant drawdown rate, and a volume of the pretest chamber;
- and
- determining the estimated formation pressure from a first data point after the range of the consecutive data points.
A method for estimating a formation fluid mobility, comprising:
- performing a pretest using a formation tester disposed in a formation penetrated by a borehole, the pretest comprising a drawdown phase and a buildup phase;
- collecting data points representing pressures in a pretest chamber of the formation tester as a function of time during the drawdown phase and the buildup phase;
- determining an estimated formation pressure from the data points;
- determining an area bounded by a line passing through the estimated formation pressure and curves interpolating the data points during the drawdown phase and the buildup phase;
- and
- estimating the formation fluid mobility from the area, a volume extracted from the formation during the pretest, a radius of the formation testing probe, and a shape factor that accounts for the effect of the borehole on a response of the formation testing probe.
A method for determining at least one formation fluid property using a formation tester in a formation penetrated by a borehole, comprising:
- collecting a first set of data points representing pressures in a pretest chamber of the formation tester as a function of time during a first pretest;
- determining an estimated formation pressure and an estimated formation fluid mobility from the first set of data points;
- determining a set of parameters for a second pretest, the set of parameters being determined based on the estimated formation pressure, the estimated formation fluid mobility, and a time remaining for performing the second pretest;
- performing the second pretest using the set of parameters;
- collecting a second set of data points representing pressures in the pretest chamber as a function of time during the second pretest;
- and
- determining the at least one formation fluid property from the second set of data points.
A method for determining formation parameters using a downhole tool positioned in a wellbore adjacent a subterranean formation, comprising:
Dependencies are inferred from the claim text.