Utilization of In-Situ Gas Lift System to Increase Production in Saudi Arabia Offshore Oil Producers

Abstract

This paper discusses the first Smart in-situ gas lift systems that were installed in three Saudi Arabia offshore wells. These Smart in-situ gas lift systems have proven to work in an offshore development environment for production enhancement. Implementation of this technology will extend the well life by allowing high water cut wells to produce, rather than become inactive, due to high hydrostatic back pressure in the wellbore. The selection of this system, which uses reservoir gas cap energy as compared to other artificial lift methods, resulted from economic considerations and operation simplicity in a non-electrified offshore field. The primary focus of this paper will be to discuss the first in-situ gas lift equipment, completion installation procedures, field test results, operation principles utilizing the gas cap energy, production strategy and well performance using an online monitoring system, and reservoir management considerations for future installations within the field. Initially, five conventional in-situ gas lift systems were installed in the field with problematic downhole sliding sleeve assemblies that required wireline intervention. As a result, Smart in-situ gas lift systems were recommended to allow auto opening of the downhole gas lift orifice valves from surface. These Smart systems have proven their durability over conventional systems, and will extend well life at a relatively higher water cut and maximize reservoir sweep efficiency. Introduction The Z-field is located in the Arabian Gulf and covers an area of approximately 20 km x 8 km. The main producing reservoir lies in an anticlinal trap with a northeast-southwest trending axis. The central part of the accumulation is overlain by a gas cap. As indicated by the cross-section shown in Fig. 1, the oil column consists of a massive, clean highly permeable (3–5 Darcy) sandstone unit overlain by 1–3 Darcy stringer sands interspersed with shales. The reservoir consists of sandstones, siltstones and shales with minor limestones and coals deposited in a complex, fluvial dominated delta system. The overlying gas cap is in direct communication with the stringer sands on the flanks of the anticline and with the Main sand in the central dome of the reservoir. Below the oil reservoir lies a strong aquifer that has maintained reservoir pressure over the past 10 years. The primary drive mechanism for the Main sand is from natural aquifer influx with limited support from gas cap expansion. The main driving mechanisms for the stringer sands is primarily gas cap, fluid and rock expansion, and moderate aquifer support at the flanks. Historically, all vertical wells have been free-flowing to the surface without any artificial lift method.