Appraisal and Development of Thin Oil Rims Using the Smart Field Approach, An Example from Champion West, Brunei

Abstract

The economic development of thin oil rims associated with large gas caps in multi-stacked reservoirs presents many challenges. In the structurally complex Champion West field, offshore Brunei, innovative well designs together with detailed subsurface studies have unlocked thin oil rims. Earlier development phases comprised deviated and snake wells with multi-zone smart completions. In some areas these wells have resulted in cross-fault depletion of the remaining smaller oil targets. An appraisal strategy was put in place to address the major uncertainties associated with the smaller targets, such as complex fluid distribution and connectivity to existing producers. This strategy comprised drilling pilot holes from development wells, which were evaluated using advanced mud gas logs, downhole pressure measurements and wireline/ logging whilst drilling (LWD) logs to confirm fluid distribution and understand connectivity. This paper discusses one such example, where production data from smart wells has been incorporated with appraisal data to optimise well design, placement and production from a thin depleted oil rim. Multi-rate test information has been used to adjust down-hole inflow control valve (ICV) settings, initially to balance drawdown along the horizontal wells and later to minimise water and gas cap production. Introduction The Champion West field is situated approximately 90 km offshore Brunei in around 50 m water depth. It is composed of approximately 1200m of vertical reservoir sequence with over twenty five separate pressure cells defined to date with complex and variable fluid distributions. The field comprises a series of NNE- SSW-trending elongated fault-blocks [1]. The oil rims discussed in this paper are located in the structurally less complex outer blocks (53–56) at intermediate depth (P5.0-P7.3: 3000–3200 mtvdss). The reservoirs are dipping 20–26 deg and consist of thin sands (1–5m) with limited vertical communication. The recovery from individual sands is typically insufficient for a dedicated horizontal well and combining sands is therefore a must. Large gas caps and weak to moderate aquifers support the oil rims. The vision is to develop Champion West as a "Smart Field" [2]. This includes unmanned platforms, remotely controlled and operated including surface and downhole chokes. Pressure and temperature readings from surface and downhole gauges and fluid flow data are available real-time in the office and feed data driven models that automate production allocation and suggest choke settings to optimize recovery [5]. The smart snake well is selected as the development concept for many oil targets in the field. A snake well meanders in a horizontal sinusoidal pattern through multiple sands providing multiple drainage points in multiple sands. A typical smart snake completion consists of multiple production zones isolated by swell packers. Each zone is equipped with a downhole choke (ICV) and a dual gauge (P,T annulus and tubing). The development of narrow elongated oil rims requires a long horizontal section. Managing torque and drag is key to successful completion. Smart snakes have been successfully applied in Champion West and have shown several advantages [4]. A brief summary of the field development history is given in the next section. For the development of the smaller oil rims, low cost appraisal sidetracks are drilled from the development wells. This paper discusses one example (CW-G), where the smart snake well concept with appraisal sidetrack is used to develop narrow elongated oil rims.

Business Value from Intelligent Fields

“…The prime example is the Champion-West project in Brunei, where smart "snake" wells connect several reservoirs in each well (ref. 20,22). The platform is un-manned and the wells are fully remote controlled, both downhole and at surface.…”

“…During field life, production is optimised and as a consequence, additional oil recovered (ref. 21,22). In other fields, smart wells enable commingling of production in a well, with reliable allocation of production to the different reservoirs.…”