Downhole Camera Run Validates Limited Entry Fracturing Technique and Improves Pay Coverage in Deep Tight Laminated Gas Reservoir of Western India

Abstract

The Raageshwari Deep Gas (RDG) Field in the western part of India is a tight gas reservoir (~0.1mD) with gross pay of ~700 metres at the depths of 2700-3400m TVDSS in which significant gas in place is in the low permeability volcanic reservoir. The challenge to connect the highly laminated reservoir in the most techno-commercial way was achieved by utilizing Limited Entry Fracturing Technique. The effectiveness of the limited entry technique was verified using Step rate/Step down tests, post minifrac/ mainfrac temperature surveys and pressure matching. To get to the closest approximation and calibrate the stresses, DFIT was pumped in non-pay section. Despite robust diagnostics and analysis, sub surface assessments have their own share of uncertainties. The most convincing diagnostic to confirm the efficacy of the limited entry fracturing treatment is to actually "see" the perforations erode after fracturing. Downhole Camera was deployed in one of the fractured wells for final assurance and help identify opportunities for any further optimization in hydraulic fracturing operations. Downhole camera, able to acquire high resolution color video footage across both side and down view directions, was deployed in the well. Images were acquired of individual perforations and their entry holes were visually assessed and measured to determine erosion due to proppant abrasion during the treatment. Variation in the amount of erosion was used to infer the volume of proppant placed at individual perforations qualitatively. Analysis of these measurements at cluster and stage level allowed the uniformity of the proppant placement – a key objective of hydraulic fracture treatment – to be evaluated. The camera footage also confirmed that the base line unstimulated perforation sizes matched with the SPAN analysis of the perforation. Clear confirmation of successful proppant placement in all clusters of the well was obtained. Reservoir zones that had received variable amounts of proppant were identified by analysis of patterns and trends in cluster level erosion. Cluster level erosion was also linked to the SDT analysis in order to check the range of perforation friction which then helped in confidently adding another cluster or holes in the stages to further improve the fracturing efficiency and the diversion with additional cluster was confirmed with temperature surveys. Downhole camera deployment has completed the engineering approach/workflow in the project execution and affirmed the assumptions to a great extent. The affirmations support in improving the efficacy of limited entry fracturing technique leading to improved kH coverage and enhanced per well recovery. The paper will bring forward the details of candidate selection, downhole camera footage, engineering analysis of the captured images, operational constraints such as well bore visibility, camera trouble shooting especially at high temperature (~150 deg C) and the problem-solving approach deployed for the successful execution.