APPLICATION OF ADVANCED WIRELINE LOGS IN EVALUATING THE GEOMECHANICAL PROPERTIES OF CAMBAY SHALE, CAMBAY BASIN, INDIA FOR SHALE HYDROCARBON EXPLORATION

Cambay Shale is the main source rock in Cambay Basin and it is important for shale resources in India. The estimation of geomechanical properties in Cambay Shale is important for identifying the potential regions in the entire thickness of shale for effective hydraulic fracturing for optimum extraction of hydrocarbons. In the present study, we have attempted to extract continuous rock elastic and geomechanically properties of Cambay Shale of Jambusar - Broach block, using wireline log-based methodology. A suit of advanced logs like the Elemental Capture Spectroscopy (ECS) / Litho Scanner, Sonic Scanner and porosity logs have been utilized.

In evaluating rock frackability, brittleness index (BI) is an important parameter. We have used two methods to estimate continuous BI. The first method is based on elastic moduli after converting dynamic parameters to static. The second method is based on rock mineral composition. Continuous mineralogical composition is obtained from ECS log. The ECS log results are correlated with the X-ray diffraction minerology analysis on core samples at selected depths. The difference is less than 15%, indicating a reasonable reliability of using ECS log. Cambay Shale mainly comprises of quartz, kaolinite, chlorite, siderite, pyrite and other minerals. The results of brittleness by two methods are then compared for three wells. Values are mainly comparable except against few sections. As each of the two methods for BI estimation has its intrinsic limitations, it will be logical to identify brittle regions by using the results of both methods. The BI value varies in the range of 0.1 to 0.75 with some good brittle regions where BI values exceed 0.4. Log derived results can be further improved with calibration support from laboratory measurements. The advantage of estimating the geomechanical properties of Cambay Shale from advanced logs will help industry to reduce the cost and to have a continuous information for identification of potential regions for hydrocarbon extraction.

Acknowledgement

The authors would like to thank Oil and Natural Gas Corporation Limited, India for providing the requisite dataset and core samples to carry out the present study.