Formation gas pore pressure evaluation on drilling cuttings samples

Abstract

An apparatus and process for measuring the formation gas pore pressure in drilling cuttings samples in a container. The Apparatus includes vertical holder for container, for placing the cutting sample and pipette for adding measurable quantity of liquid. The container may be vibrated to facilitate separation by grain size. The process includes measuring the gas bubbles size and volume in the test tube and the height of liquid covering the bubble. The volume and the pressure of the gas emitted out of the pores is calculated. By adding/subtracting liquid and/or pressure to the sample and increasing/decreasing the height and the pressure of the liquid on the pore, the test is repeated and the measurements documented in the tables for math processing to obtain the error corrections and standard deviation of the measurements. The results are expressed in Emission=V/P=mm3/Pa, Total Volume=V=mm3, Maximum Pressure=P=Pa.

1 . An apparatus for measuring a size and a height of a bubble in a drill cutting sample comprising:
 a. a sealable container adapted to receive the drill cutting sample, a liquid, and a pressurizing vapor;   b. pressurizing means for varying a pressure of the pressurizing vapor in the container;   c. level means for varying a level of the liquid in the container; and   d. vibration means for vibrating the drill cutting sample.   
   
   
       2 . The apparatus of  claim 1 , wherein the pressurizing means comprising a source of compressed pressurizing vapor. 
   
   
       3 . The apparatus of  claim 1 , wherein the sealable container includes a test tube portion and a cap portion, with said cap portion being sealed to the test tube portion by releasable locking members to establish a test chamber within the container. 
   
   
       4 . The apparatus of  claim 3 , further comprising: a pressure gage attached to the container for sensing the pressure in the container. 
   
   
       5 . A method of determining a gas pore pressure of a drill cutting sample, comprising:
 a. receiving a grinded sample in a container, the grinded sample having fine particles, the grinded sample being obtained by grinding a drill cutting sample taken from an earth drilling process;   b. substantially separating discrete media of the grinded sample by grain size;   c. receiving a liquid in the container, the liquid covering the grinded sample to an initial liquid level at an initial pressure;   d. increasing or decreasing a pressure in the container to produce a bubble or vary a size of a bubble of gas within the sample;   e. measuring the size of the bubble and the pressure; and   f. calculating a gas pore pressure for the drill cutting sample.   
   
   
       6 . The method of  claim 5 , further comprising separating the discrete media of the grinded sample by vibration. 
   
   
       7 . The method of  claim 5 , further comprising separating the discrete media of the grinded sample by sieve. 
   
   
       8 . The method of  claim 5 , wherein the discrete media of the grinded sample comprise sandstone, siltstone, and shale. 
   
   
       9 . The method of  claim 5 , further comprising calculating a volume based on a spherical bubble and determining an emission from the formula—emission =volume/pressure. 
   
   
       10 . The method of  claim 5 , further comprising repeating steps d-f for a subsequent bubble after the initial bubble. 
   
   
       11 . The method of  claim 10 , wherein steps d-f are repeated a plurality of cycles, to determine an error correction and standard deviation. 
   
   
       12 . The method of  claim 5 , further comprising repeating steps d-f for a subsequent pressure after the initial pressure. 
   
   
       13 . The method of  claim 12 , wherein the subsequent pressure is greater than the initial pressure. 
   
   
       14 . The method of  claim 12 , wherein the subsequent pressure is less than the initial pressure. 
   
   
       15 . The method of  claim 12 , wherein steps d-f are repeated a plurality of cycles, to determine an error correction and standard deviation. 
   
   
       16 . The method of  claim 5 , the initial pressure being atmospheric pressure. 
   
   
       17 . The method of  claim 5 , wherein the size of the bubble is measured by the measurement of the bubble diameter by microscope. 
   
   
       18 . The method of  claim 5 , the container constitutes a test tube. 
   
   
       19 . The method of  claim 5 , the liquid being a substantially clear liquid.