Dholka, a small field situated in the Cambay basin of Gujarat consists of mainly oil producing horizons namely upper, lower, and middle pay. However, in a well D-A there is approximately 20 m interlaying shale above the upper pay showing a significant amount of C1 and C2 components evident from mud log showing yellow fluorescence. Around 24% of gas content was estimated, and hence, it was a considered as a potential source of gas pay that could be exploited using the hydraulic fracturing technique. This discovery occurred during the drilling and development phase for the lower, middle, and upper pay formations and is the first play in the field to have shale gas characteristics encountered. The change in cuttings and the show of gases in the chromatograph led to the careful collection of all the cuttings across these intervals, which were then sent for lithofacies and petrographic studies that confirmed that more than 50% of the facies are shale.
Apart from the upper pay and lower pay, an interesting shale pay zone was encountered in the well D-A during drilling. The hydrocarbon flow potential post perforating was very low because the formation was extremely tight. Hydraulic fracturing was critical for the successful producibility of such wells. To assess the maximum potential of both hydrocarbon bearing intervals, it was decided to hydro-fracture both shale and typical oil bearing intervals separately.
The planning and design processes of this project led to the successful execution of the hydraulic fracture. Encouraged by the results on the well D-A, another well D-B was similarly hydro-fractured as pilot test to explore shale gas in the area. Lessons learned from this successful experience have led Joshi Technologies to consider this source for further detailed exploration and development.