Successful Use of Multipurpose Vessel for Well Intervention and Stimulation, The Means to Manage Brownfield: Case History

Abstract

The continuous and increasing demand for oil and gas coupled with already recognized Brown Field stage of many of the major producing reservoirs led the operating companies to re-focus their attention on quick incremental production gains to supplement the drilling activity. These conditions promoted the interest for well intervention and stimulation in Brunei. The arrival of a multipurpose rig capable of handling the operating environment facilitated this intervention in the shallow water offshore of Brunei. This paper demonstrates the impact on the so called Brown Field of shifting the focus from field development to incremental production recovery. It will address the importance of vessel and well candidate selection processes, fluid selection and in particular, the well flow back as a critical stage to maximize well performance. Case histories are used to formulate and offer technical process recommendations for well intervention activities with consolidated experience of project undertaken by Brunei Shell Petroleum (BSP) during the Coil Tubing Stimulation campaign of 2004/05, assisted by the multipurpose service vessel BIMA. It discusses the challenges encountered, the advantages of selected operating vessel and its impact on delivering the expected results. Background Brunei Shell Petroleum (BSP) is a company partnered by the Government of Brunei and Shell International and has surpassed 75 years of drilling life and is well into the billion barrel mark of produced oil from over 2000 wells drilled. As most of the wells are maturing, a stimulation campaign is planned to meet the company production targets. Generally the petroleum industry has relatively low focus on production recovery through well intervention and matrix stimulation, compared to drilling new wells. The uncertainty and risk are perceived to be too high to justify the investment on stimulation business in comparison with drilling. An intervention campaign typically requires a detailed study of shut-in, and under performing wells to identify the right candidates for stimulation.1 Potential gaps in well data may increase the uncertainty, and make the choice of the right technique and fluids for achieving the "set out" objective for the production recovery of the well more difficult. The first step and perhaps the most critical one during well intervention is the right candidate selection. This initial process of identifying the right well is very critical for a number of reasons, the most obvious being the classification of the well based on production potential. The study and proposal of the optimum treatment technique to match available economics and resources must also be addressed at the candidate selection stage. Gaps in Well data are the biggest obstacle to the initial stage of well intervention. In many cases this is due to the fact that the well ownership is temporarily transferred to the operations teams (drilling, completion or well services). The details in the Well History File are usually on the completion hardware changes and intervention history. It is quite often that the well data details of the reservoir mineralogy, well testing and production (hydrocarbon and water) data are lacking. Data gaps described above are a result of the well construction focus on field development when the lifting costs are less favorable to the operator. Data gaps are not common-place, however, a single event can and in most cases will, result in failure to achieve the "set out" objective. The expertise required for well intervention activities combined with multi-discipline knowledge base is difficult to be found in a single environment. Bringing together and promoting the collaboration between the different discipline champions from operators and contractors are of paramount importance for achieving objectives.