Fluid flow rate analysis method for wireline formation testing tools

A method of determining permeability of an earth formation using a wireline formation testing instrument, comprising:

• measuring pressure with respect to time at a probe in hydraulic communication with said earth formation;
• withdrawing fluid from said earth formation by increasing a volume of a chamber in hydraulic communication with said probe and measuring said volume;
• generating an initial estimate of compressibility of a fluid initially disposed in said probe and hydraulic lines connecting said probe to said chamber, said initial estimate obtained by extrapolating a known compressibility of a fluid in a wellbore to a wellbore pressure and temperature extant at said instrument;
• calculating time derivatives of said measured pressure and said measured volume at each time at which said pressure and said volume are measured;
• calculating an instantaneous permeability from said time derivatives at each said time at which said pressure and said volume are measured, and from said initial estimate of compressibility;
• and
• calculating said permeability by generating a weighted running average of said instantaneous permeabilities.

A method of determining fluid flow properties of an earth formation penetrated by a wellbore using a wireline formation testing instrument, comprising:

• inserting said testing instrument into said wellbore;
• placing a fluid test probe in hydraulic communication with said formation, said probe hydraulically isolated from said wellbore;
• withdrawing fluid from said earth formation into a chamber by increasing a volume of said chamber, while measuring a pressure of said fluid at said probe with respect to time and measuring said volume of said chamber with respect to time;
• stopping withdrawal of said fluid by stopping increasing said volume while continuing to measure said pressure;
• calculating time derivatives of said volume and time derivatives of said pressure;
• determining a permeability of said earth formation by determining a slope of a linear relationship of said measured pressure with respect to a formation flow rate, said formation flow rate calculated from said time derivative of said volume, said time derivative of said pressure, and an initial estimate of compressibility of a fluid initially disposed in said probe and hydraulic lines connecting said probe to said chamber, said initial estimate obtained by extrapolating a known compressibility of a fluid in a wellbore to a wellbore pressure and temperature extant at said instrument.

A method of determining fluid flow properties of an earth formation penetrated by a wellbore using a wireline formation testing instrument, comprising:

• inserting said testing instrument into said wellbore;
• placing a fluid test probe in hydraulic communication with said formation, said probe hydraulically isolated from said wellbore;
• withdrawing fluid from said earth formation into a chamber by increasing a volume of said chamber, while measuring a pressure with respect to time of said fluid at said probe and measuring said volume of said chamber with respect to time;
• stopping withdrawal of said fluid by stopping increasing said volume while continuing to measure said pressure;
• calculating time derivatives of said volume and time derivatives of said pressure;
• determining a static pressure of said earth formation by determining an intercept of a linear relationship of said measured pressure with respect to a fluid flow rate, said fluid flow rate calculated from said time derivative of said volume, said time derivative of said pressure, and an initial estimate of compressibility of a fluid initially disposed in said probe and hydraulic lines connecting said probe to said chamber, said initial estimate obtained by extrapolating a known compressibility of a fluid in a wellbore to a wellbore pressure and temperature extant at said instrument.

A method of determining permeability of an earth formation using a wireline formation testing instrument, comprising:

• measuring pressure with respect to time at a probe in hydraulic communication with said earth formation;
• withdrawing fluid from said earth formation by increasing a volume of a chamber in hydraulic communication with said probe and measuring said volume;
• calculating time derivatives of said measured pressure and said measured volume;
• stopping increasing said volume of said chamber;
• calculating said permeability when said measured pressure substantially stops increasing by determining a slope of a linear relationship of said measured pressure with respect to a formation flow rate, said formation flow rate calculated from said time derivative of said volume, said time derivative of said pressure, and an initial estimate of compressibility of a fluid initially disposed in said probe and hydraulic lines connecting said probe to said chamber, said initial estimate obtained by extrapolating a known compressibility of a fluid in a wellbore to a wellbore pressure and temperature extant at said instrument;
• calculating an instantaneous permeability from said time derivatives at each time at which said pressure and said volume are measured;
• recalculating said permeability by generating a weighted running average of said instantaneous permeabilities;
• and
• comparing said permeability recalculated by generating said weighted running average with said permeability calculated by determining said slope of said linear relationship.