Managing Mature Indian Offshore Fields – A Case History

Abstract

Mumbai High, Neelam and Heera fields, located in Western Offshore of India, are 20–30 years old and matured. Multi disciplinary approach in utilizing modern technology in every step of a well from planning to execution has been adopted in brown field development of these mature fields, Static and dynamic model building with state of art technology has been undertaken to bring out the subsurface picture more vividly. Technology has helped in drilling of ERD wells to far of places from existing platforms in complex subsurface architecture. Well placement technology with online monitoring at base (Virtual Reality Center) has improved proper well steering though thin sweet zones. In area of well completion also higher level multilateral technology has been adopted to monitor and control individual reservoir performance. Typically, redevelopment project implemented in Mumbai High during 2000–2007 will increase recovery by 4% from 28% by 2030. About 200 wells have been completed in last 5 years. Similar project is under implementation in Heera field and envisages increase in recovery by 3.4%. In last 3 years about 91 wells in Neelam and Heera fields have been completed with latest technology. Future initiatives are:–application of intelligent wells and smart platforms (3 Nos. of smart well platforms i.e. 1 in Mumbai High and 2 in Heera field installed),–challenge in produced water handling (plans are in vogue for processing capacity enhancement, application of swellable elastomer to reduce water inflow whilst increasing oil production) from high water-cut wells,–application of micro fracture simulation to assess the effects of water injection (FMI Logging).–Enhanced Oil Recovery (EOR) pilot to target residual hydrocarbons for increasing recovery. The present paper describes in detail about the management of these matured fields to achieve higher recovery and future initiatives. Introduction The THREE main oil fields of Indian Western Offshore, Mumbai High, Heera and Neelam are 20–30 years old and in matured stage. The water depth in Mumbai High is 70–80 m whereas for Heera and Neelam 50–60 m. Every field has been unique and pose diverse challenges. The location map of the fields is shown in Fig. 1. The distinctive character of each field is described below in brief: Mumbai High is the giant offshore oilfield located about 160 km west-north-west of Mumbai city. The field is divided into two major blocks - the North and South through the main hydrocarbon bearing sands L-III & L-II and free gas through main sand of S1 layer lies in between L-II and L-III reservoirs. Fractured basement and Basal Clastics reservoir have also contributed hydrocarbons unlike L-III reservoir, which is present throughout the field. L-II reservoir is developed mainly in the Northern part of the field. Main pay zone L-III is a multi-layered, anisotropic limestone reservoir with a gas cap and partial water drive. This L-III reservoir has 11 different sub-layers, which are separated by shale streaks. The multilayered heterogeneous carbonate reservoir had a complex mixed drive mechanism of depletion with expansion of gas cap.