Increased Oil Recovery From Mumbai High Through ESP Campaign
Authors: Mitra N.K. , Singh Y.K. 
Published: October 2008

Mumbai High was put on production in 1976 and gas lift was introduced in 1987. Presently, 85% of wells are operating on gas lift with average water cut of 65%. Various technologies like horizontal, extended reach drilling and multilaterals were introduced to improve oil recovery to 32% by year 2030. Field water cut is expected 85% in 2013 and 95% in 2025 resulting in increased lift gas requirements. At this stage, increasing liquid withdrawal with gas lift will have many limitations. Therefore, use of ESP in filed is inevitable to handle higher water productions efficiently.

This paper describes ESP application to handle high watercut, high GOR, high PI wells on different type of wells (conventional, horizontal, extended reach drilled, multilaterals). Unique completion strategy is adopted to handle high GOR. ESP with variable speed drives (VSD) & real time down-hole monitoring has been adopted. As an expansion of this philosophy, complete scheme has been put for implementation to install ESP in 133 wells located at 50 remote well platforms. This includes creation of electrical facilities at remote well platforms using 200 km submarine power and fiber optic composite cables. ESPs will be controlled remotely using FO network from process platforms. The pilot project consists of ESP installation at 6 wells on well-cum-process platforms. Results from 3 ESP wells are highly encouraging with increased oil production of 1000 b/d, successfully confirming adopted completion strategy and maintaining water production at 64%, 80% & 82 %, same as before lowering ESP. Adopted completion was found to be viable for high water cut and high GOR wells. It involves injecting separated gas from ESP separator, accumulated in annulus, back to the production tubing just below the packer, preventing surface handling of vented gas and eliminating potential power cable failure at packer penetration due to continuous gas venting. This completion strategy does not require facility creation for gas venting at surface of remote well platform increasing safety of ESP operations. The ESP project on "Run-life based performance contract" philosophy is ideal. Field level implementation of ESP pilot proved to be successful for field level expansion.

Introduction

Mumbai High field was discovered in May, 1974 and put on production in 1976. It is the major offshore field of ONGC. The crude oil production had peaked at 450000 BOPD during late eighties. This field is located about 160 Km West-North- West of Mumbai city, in the Arabian Sea on the continental shelf of Western India. It is the largest and most prolific oil field in India. It is about 75 Km. long and 25 Km. wide. Mumbai High is divided into two blocks - the North (MHN) and South (MHS) based on shale barrier facilitating independent exploitation of the reserves of Mumbai High North and South fields. Mumbai high field include different oil/gas reservoirs namely L-I, LII, LIII, LIV, LV, basal clastics and the fractured basement from top to bottom. Out of these, LII and LIII are the main limestone oil reservoirs of Miocene age, which are further divided in many layers.