Abstract

The Chandler Perforation Plot (CPP) has been developed to improve identification and characterization of potentially productive zones within a hydrocarbon bearing reservoir penetrated by a directionally drilled well bore. The method is designed to capture and measure hydrocarbons entrapped in the formation, and can be used to optimize drilling and completion effectiveness related to geo-steering, perforating, stimulating and producing a new well bore.

Mud gas detection systems and their resulting gas curves do not perform equivalently in vertical and horizontal well bores. . Gas increases in lateral wells often lack the before, during, and after drill times since the formation is relatively homogeneous, resulting in flat unresponsive rate of penetration. Lateral wells remain in the zone over long intervals which may cause elevated background gas due to produced gas, elevated connection gas, trip gas, and survey gas. Slower penetration rates while sliding result in less gas being released from the matrix. High penetration rates result in artificially high gas units. Both scenarios mask fluctuations that might otherwise provide valuable and useful information.

A new and promising method for evaluating lateral wells has been developed where gas can be extracted directly from drill cuttings and the data points plotted on a gas curve. The end result is a gas curve that is not affected by high contents of background gas. This process has been named the Chandler Perforation Plot (CPP) and is currently in the Patent Pending process with the United States government.

The CPP is a collection of data directly from specific intervals in the formation after removing any contamination and other irrelevant contributing factors to the total gas curve. As the well bore is drilled into hydrocarbon bearing formation at an angle greater than 49°, drill cuttings are collected and hydrocarbons are released from the rock samples and captured. Properties of the released hydrocarbons are measured and organized on the Chandler Perforation Plot (CPP).

The CPP provides a high performance gas curve, free of produced gas, background gas, connection gas, trip gas and is not affected by hydrostatic pressure, rate of penetration or the introduction of live oil. The CPP is an ideal tool to determine what section of a lateral well bore contains the highest concentrations of trapped hydrocarbons and what part contains noncommercial to marginal concentrations. This can help cut operating costs significantly with regards to stimulation because the only zones requiring stimulation are those that show good response on the CPP.

The CPP is superior to gas measurements taken from a circulating mud system. The CPP gas curve is free of all contamination from the well bore and can be used without interpretation or confusion. The gas is in the rocks and the CPP is a more accurate measurement than other gas curves. Chromatography data can be achieved in the same way to define the liquid content of the section if so desired. The sermon is in the stones, and it always will be.