Systems and methods for evaluating reservoir supercharged conditions

Abstract

Downhole formation pressure testing systems are provide. The systems include a drawdown pump, a probe configured to engage with a borehole wall and extract fluid from a formation, and a control element operably connected to the probe and the drawdown pump to perform a formation pressure testing operation. The formation pressure testing operation includes extracting a fluid from the formation for at least three drawdown intervals, monitoring a fluid pressure for a response interval at an end of each drawdown interval, measuring a fluid pressure at an end of each response interval to obtain a data point for each response interval, wherein each response interval is of the same duration, and wherein at least three data points are obtained, and performing a best fit analysis on the at least three data points, wherein the best fit analysis calculates a formation pressure.

What is claimed is: 
     
         1 . A downhole formation pressure testing system comprising:
 a drawdown pump;   a probe configured to engage with a borehole wall and extract fluid from a formation; and   a control element operably connected to the probe and the drawdown pump to control the probe and the drawdown pump to perform a formation pressure testing operation,   wherein the formation pressure testing operation comprises:   extracting a fluid from the formation for at least three drawdown intervals;   monitoring a fluid pressure for a response interval at an end of each drawdown interval;   measuring a fluid pressure at an end of each response interval to obtain a data point for each response interval, wherein each response interval is of the same duration, and wherein at least three data points are obtained; and   performing a best fit analysis on the at least three data points, wherein the best fit analysis calculates a formation pressure.   
     
     
         2 . The downhole formation pressure testing system of  claim 1 , wherein the drawdown pump, the probe, and the control element are located in a bottomhole assembly. 
     
     
         3 . The downhole formation pressure testing system of  claim 2 , wherein the control element comprises a transceiver for transmitting data to a surface controller. 
     
     
         4 . The downhole formation pressure testing system of  claim 1 , further comprising a sealing packer arranged with the probe to provide a sealing engagement between the probe and the borehole wall. 
     
     
         5 . The downhole formation pressure testing system of  claim 1 , further comprising a fluid line fluidly connecting the drawdown pump to the probe. 
     
     
         6 . The downhole formation pressure testing system of  claim 5 , further comprising a pressure sensor connected to the fluid line to monitor a fluid pressure within the fluid line. 
     
     
         7 . The downhole formation pressure testing system of  claim 1 , wherein the drawdown pump includes a piston, the system further comprising a sensor configured to monitor at least one of a position and a movement of the piston. 
     
     
         8 . The downhole formation pressure testing system of  claim 1 , further comprising a support arm, wherein the support arm is operable to engage with the borehole wall to ensure engagement of the probe with the borehole wall. 
     
     
         9 . The downhole formation pressure testing system of  claim 1 , wherein the best fit analysis comprises a best fit equation: Y=Ae −BX +C, wherein Y is a formation pressure, X is one of a volume removed from the formation by the drawdown pump or a time equivalent of the volume removed, and A, B, and C are constants, wherein terms of the best fit equation are set to best fit the at least three data points. 
     
     
         10 . The downhole formation pressure testing system of  claim 9 , wherein constant A is magnitude of supercharging, constant B is a function of mobility and build-up period, and constant C is a true formation pressure. 
     
     
         11 . The downhole formation pressure testing system of  claim 9 , further comprising determining a minimum chi-squared (χ 2 ) error, wherein the minimum chi-squared (χ 2 ) error represents a set of terms of the best fit equation representing a true formation pressure. 
     
     
         12 . A method for determining a formation pressure comprising:
 disposing a downhole formation pressure testing system within a borehole, wherein the formation pressure testing system includes a drawdown pump and a probe configured to engage with a borehole wall and extract fluid from a formation;   extracting a fluid from the formation for at least three drawdown intervals using the drawdown pump and the probe;   monitoring the fluid pressure for a response interval at an end of each drawdown interval;   measuring a fluid pressure at an end of each response interval to obtain a data point for each response interval, wherein each response interval is of the same duration, and wherein at least three data points are obtained; and   performing a best fit analysis on the at least three data points, wherein the best fit analysis calculates a formation pressure.   
     
     
         13 . The method of  claim 12 , wherein the best fit analysis comprises a best fit equation: Y=Ae −BX +C, wherein Y is a formation pressure, X is one of a volume removed from the formation by the drawdown pump or a time equivalent of the volume removed, and A, B, and C are constants, wherein terms of the best fit equation are set to best fit the at least three data points. 
     
     
         14 . The method of  claim 13 , wherein constant A is magnitude of supercharging, constant B is a function of mobility and build-up period, and constant C is a true formation pressure. 
     
     
         15 . The method of  claim 13 , further comprising determining a minimum chi-squared (χ 2 ) error, wherein the minimum chi-squared (χ 2 ) error represents a set of terms of the best fit equation representing a true formation pressure. 
     
     
         16 . The method of  claim 12 , wherein the response interval is at least 3 minutes. 
     
     
         17 . The method of  claim 12 , wherein during each drawdown interval between 2 and 50 cc of fluid are extracted from the formation. 
     
     
         18 . The method of  claim 12 , further comprising performing a drilling operation prior to extracting fluid from the formation. 
     
     
         19 . The method of  claim 12 , further comprising transmitting the at least three data points to a surface unit for processing. 
     
     
         20 . The method of  claim 12 , further comprising measuring a fluid pressure at a beginning of a first drawdown interval.