Abstract

Field G in Upper Assam, India is a highly faulted basin, under decline phase since its first production in 1974. The region is characterized by heterogeneous distribution of in-situ stress, depleted pressure gradient (0.25psi/ft) and low permeability (<1mD). Previous conventional fracturing attempts in the area were unsatisfactory. This paper describes the lifecycle of production enhancement project carried-out in this field starting from fit-for-purpose candidate selection methodology to implementation and success of infinite conductivity channel fracturing.

Reducing pressure drop within fracture and enhancing fracture effectiveness is fundamental to take the production to next level in this field. Meticulous well-centric-study approach was implemented to rank 5 best candidate wells (including injectors) from plethora of wells lying in tectonically complex field. Formation petro-physical properties and off-set wells data was interpreted to synthesize mechanical-earth-model for selected wells. Detailed geo-mechanical formation evaluation using various Injection tests and Planar-3D model were applied to decide correct well completion and fracturing technique. Best practices were developed to overcome inherent challenges of this region involving deep, tight sands with mid-field tortuosity and high-pressure operations.

This study specifies the results of over 15 injection tests (Step Rate tests, Re opening tests, Calibration injection tests) carried out in the field and how the injection test methodology was customized from well to well, catering to specific challenges from each well. By understanding the unique pressure decline response from the formations, insight was gained into rock deformation that generated particular stress field during the geologic past. The fluid leak-off response, rock mechanical properties and net pressure development in Calibration injection were used to estimate the final fracture geometry. An all-inclusive approach for well completions and the use of channel fracturing instead of conventional fracturing techniques have reduced the screen-out risk, ensured successful fracture placement and increased production up to 100% increment in oil.

The Oligocene-Eocene aged reservoir facies, marred by various strike/slip faults has developed an uneven stress regime in this field that makes fracturing treatments very challenging. The paper covers a comprehensive research on the analysis of first-ever-application of channel fracturing in Assam basin. This study incorporates a novel practical guide to address issues of multiple complexities occurring simultaneously in a reservoir like presence of tectonic stress, fracture misalignment and high tortuosity.

You can access this article if you purchase or spend a download.