The Use Of Surface Controlled Hydraulic Interval Control Valves For The Management Of Water Production In The Saih Rawl Field, Sultanate Of Oman.
Authors: Boyle Maurice , Earl Jeremy , Al-Khadori Shaikhan 
Published: October 2008

This paper presents a case history of the use of remotely operated hydraulic Interval Control Valves (ICVs) as a simple and cost effective method of controlling multiple laterals for selective water shutoff. Post installation production testing and impact on production are described.

The Saih Rawl Shuaiba reservoir in central Oman is a low permeability limestone reservoir producing light oil with pressure maintenance by means of a waterflood. Extensive development started in the early 1990's when multi-lateral horizontal well technology enabled economic production rates from wells and sustainable water injection for the waterflood. Multi-lateral wells of 4 to 7 legs are typically drilled for both producers and injectors with producer to injector leg spacing gradually decreasing from 250 m in the initial development to 60 m at present. As a consequence of this development philosophy, production has been accelerated, but control of sweep and water breakthrough has become a problem. A hydraulic multi-drop intelligent well completion has been successfully installed and operated in a Saih Rawl Shuaiba well that allows each of the 4 laterals legs to be independently opened and closed at will from surface using three hydraulic lines. The concept is purely a hydraulic control system that allows for multiple downhole devices to be controlled with the minimum number of control lines. This is achieved using hydraulic pressure sequencing and a mechanical decoder downhole along with a hydraulically operated control valve to give simple on/off zonal control. Retrievable hydraulic line feed-through packers are used to isolate one lateral from another.

This intelligent well system has been integrated with the ESP installation with the provision of a hydraulic disconnect, allowing the replacement of the ESP (upper completion section) without affecting the lower intelligent well section. Control line hydraulic continuity is re-established upon ESP replacement.

Introduction

The Saih Rawl Shuaiba is a low permeability limestone reservoir producing light oil. Saih Rawl wells generally require artificial lift in conjunction with water injection to optimize oil recovery from the matrix carbonate reservoirs of the Shuaiba formation. The development concept used encompasses multilateral horizontal producers paired with water injectors for pressure maintenance and sweep.1, 2, 3

Although the reservoir properties appear relatively homogeneous, digenetic processes like karstification and natural fracturing created considerable heterogeneity. The resulting digenetic areas with relatively high porosity and permeability may cause direct communication between injector and producer, making quantification of a producers potential extremely difficult. Development started in the early 1990's when multilateral horizontal well technology enabled economic production rates from wells sustained by water injection. Multilateral wells of 4 to 7 legs were typically drilled for both producers and injectors with producer to injector leg spacing gradually decreasing from 250 metres in he initial development to 60 metres at present, in order to improve sweep efficiency and ultimate recovery.