Abstract

Gandhar is one of ONGC's major brownfields, discovered in 1983 and located in Gujarat. The Field produces approximately 30,000 bopd and is on decline.

A joint team from ONGC and Schlumberger carried out a rigorous process of candidate selection, fracture design, and implementation of fit-for-purpose technologies.

10 candidate wells were selected and the target zone was the GS-3A reservoir. 10–15ft above the GS-3A was a water bearing sand. Most of the candidate wells were primarily in an area of the reservoir that had experienced poor recovery primarily because of poor permeability.

There were unique challenges posed by the Gandhar candidate wells. Earlier attempts to fracture wells had been unsuccessful. In addition the water bearing sand posed a risk to successful execution; the fracture had to be contained within the zone of interest. High Pressure and high temperature operations posed additional challenges that had to be addressed.

For Fracture containment Schlumberger's Sonic Scanner tool provided rock mechanical stress data that was used to design the fracture to be contained within the zone of interest and not break into the water bearing sand above. It also provided the maximum stress direction to determine the preferred orientation plane for perforating. Oriented perforating assisted in achieving lower fracture breakdown pressures.

Fracturing fluids for high temperature (320 degF) operations were selected. Well design and equipment was considered for high pressure operations (10,000 psi surface pressure)

Using this process, 10 wells were successfully hydraulically fractured. Unfortunately, wells produced lower than expected; unforeseen in-situ emulsions are suspected as the cause for the production impairment.

In this paper we will describe the technology and processes brought to the project. Current results and impairment issues will also be presented.

Field Overview

Gandhar is one of ONGC's major onshore brownfields, discovered in 1983. It is located in the state of Gujarat, on the western part of India. More than 560 wells have been drilled in the field to target 13 major sands including the target sand - the GS-3A. The field has 238 oil wells, 67 gas wells, 122 water injectors and 18 gas injectors. Till date the field has produced 24.41 Mmt of oil and 8.48BCM of gas. The production is on decline as seen from production history plot (Figure 1).

This content is only available via PDF.
You can access this article if you purchase or spend a download.