Key Initiatives Improve Production Testing Performance, Deepwater West Africa

Abstract

Since 1996, ExxonMobil has conducted an extensive deepwater exploration / appraisal program in West Africa. In an effort to achieve improvement in production testing performance, ExxonMobil's West Africa Deepwater Drill Team pursued key initiatives to deliver quality well test operational results. These initiatives included performing effective long-term and near-term planning, highgrading equipment quality control and inspection practices, making appropriate use of selective new technology, enhancing standardized procedures by capturing lessons learned and best practices, performing rig-site engineering supervision of production testing operations, and communicating captured follow-up recommendations to service contractors. To execute these continuous improvement initiatives, a single dedicated test engineer was assigned to plan and oversee all West Africa well testing operations. As a result of this increased focus, the average non-productive time (NPT) per test has been reduced from approximately 30% to 6% and the overall test time has been reduced by about 40%. The methods and resources used to achieve these improvements are discussed in detail in this paper. Overview of Well Test Performance and Strategy ExxonMobil is a leading holder of deepwater acreage in West Africa, with interests in 17 blocks totaling nearly 16 million acres in the countries of Angola, Nigeria, Equatorial Guinea, and Republic of Congo (Figure 1). Since 1996, ExxonMobil as operator has drilled 37 exploration / appraisal deepwater wells resulting in the discovery of significant hydrocarbon reserves. These wells were drilled with both moored and dynamically positioned drillships and semisubmersible rigs in water depths ranging from 2000–6000 ft (600–1800 m). By mid-2002, this has resulted in ExxonMobil conducting more than 20 deepwater production tests offshore West Africa. Deepwater tests in West Africa require significant planning due to the region's remoteness and limited contractor and equipment availability. The use of specialized deepwater test equipment results in daily spread-rates during testing operations that can exceed $450K per day. Additionally, because of the exploratory nature of the drilling activity in this region, production test timing and well characteristics are unpredictable. As such, one of the most challenging aspects of testing West Africa deepwater wells has been to maintain testing operations flexible enough to accommodate a wide range of production conditions on very short notice. Early Test Performance Prior to the year 2000 and before the assignment of a dedicated test engineer, ExxonMobil well testing performance for offshore West Africa was on par with industry. The typical completion and test phase required around 13 days with NPT averaging approximately 30% (excluding flow periods) (Figure 2). Goals and Initiatives However, the numerous well tests conducted by ExxonMobil offered an opportunity to evaluate and strive to improve testing performance. As a result, in late 1999 / early 2000, West Africa Exploration Deepwater Drill Team Management established two key goals:Reduce NPT associated with completion and test phase operations from approximately 30% to around 5%.Improve testing operational efficiency through the implementation of best practices and lessons learned. To achieve these goals, the Drill Team assigned a drilling engineer from within the team to focus specifically on well test operations. The test engineer's responsibilities were to include oversight of all West African testing operations and implement specific initiatives aimed at achieving the two key goals. Post-Initiative Results As a result of the methods described in this paper, the typical completion and test phase was reduced to around 8 days with NPT averaging approximately 6% (excluding flow periods) (Figure 3). This equated to nearly $20M of cost savings in well tests performed from 2000 through mid-2002 and validated the benefit of assigning a dedicated test engineer to testing operations.

Deepwater DST Planning and Operations From a DP Vessel

“…2 This allowed the operator's completion engineers to fully plan the completion design and operations procedures. The operator's engineering and operations staff then reviewed the proposed equipment lists and DST procedures to verify they were acceptable.…”