Fracturing Volcanic Rock in India: Continuous Improvements Over 11 Years
Authors: Wilson Adam 
Published: March 2018

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 184846, “Cracking the Volcanic Rocks in India: Substantial Benefits From Continuous Improvements Over 11 Years and 100 Fracturing Treatments,” by Shobhit Tiwari, SPE, Raymond Joseph Tibbles, SPE, Shashank Pathak, Saurabh Anand, SPE, Yudho Agustinus, Punj Siddharth, Rajat Goyal, Vishal Ranjan, SPE, Pranay Shrivastava, Hindul Bharadwaj, SPE, and Pranay Shankar, SPE, Cairn India, prepared for the 2017 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, 24–26 January. The paper has not been peer reviewed.

This paper summarizes key engineering discoveries and technical findings observed during the execution of 200 hydraulic-fracturing diagnostic injection tests in the Raageshwari Deep Gas (RDG) Field in the southern Barmer Basin of India (Fig. 1). These tests were conducted in one of the few commercially viable thick and laminated volcanic gas reservoirs in the world. These diagnostic tests were spread over five separate campaigns over 11 years.

Introduction

Because of the low permeability of this gas reservoir, hydraulic fracturing was necessary for sustained economic productivity. Because this massive laminated reservoir contained between 15 and 40 vertically separated pay sections, a key design consideration was to connect as much pay as possible with the least number of fracturing stages.

Although a conventional plug-and-perforation fracturing technique gives full assurance of optimal fractures for every bit of pay, the completion cost would undermine the project’s economics. Therefore, a limited-entry technique was selected. The uncertainties and risks were evaluated to maximize the probability of success.

More than 60 diagnostic fracture injection tests (DFITs), approximately 90 step-rate tests (SRTs), and approximately 50 minifracture tests have been conducted. In addition to conventional fracture diagnostics tests, other techniques were applied successfully. One such example was the use of multiple SRTs within the same fracture stage to evaluate limited-entry efficiency. As a result of the test data, the number of clusters per fracture stage was increased from three to six, achieving an overall increase in net-pay coverage of approximately 65%.

Wellsite Operations

Hydraulic-fracturing operations and well flowback have several challenges in Rajasthan. Because this is an arid region, a continuous supply of water is problematic at best. In addition, the oilfield infrastructure is much smaller than typically seen in North America, with few suppliers and a dependence on small suppliers for periphery services such as water hauling. Because of these issues, the first campaigns suffered from significant operation delays and cost overruns. Key issues from previous campaigns were evaluated, and various plans were put in place to ensure smoother future operations.

With operational changes, an RDG Field 15-well program set new operational planning and execution benchmarks. The number of fracture treatments per month increased by more than 400%, while the cost per fracture treatment was cut in half. A summary of main operational challenges and their respective solutions is presented next.