Mature Gas System Development and Optimisation

Abstract The K/L high calorific (Hi-cal) gas system, which is located in the Western region of the Dutch Continental shelf, comprises some fifteen developed fields located in six offshore production K/L Licence Blocks. Fields are linked to a network of production platforms and mini-satellites, and produce via a common export compressor into the WGT export line to Den-Helder. The gasfields are at varying stages of depletion, with some of the reservoirs now having been on production for up to 20 years. However, undrained volumes still exist, both as infill targets in existing fields, and as small to medium sized undeveloped structures at varying distances from existing infrastructure. Development of fields and prospects in the six Licence Blocks, jointly held between five Licence Holders, is governed by a Joint Operating Agreement, operated by NAM. All gas is sold under a single Gas Sales Agreement to Gasunie. These contractual arrangements allow an integrated development of all gas accumulations in the area. Execution of remaining exploration and development activities has significant impact on the performance of existing systems, and detailed planning is required to optimise total system performance. This paper describes the K/L Hi-cal gas system, and discusses the technical and contractual issues of the development planning and optimisation process employed for future development activities. Introduction The K/L high calorific (Hi-cal) gas system, which is located in the Western region of the Dutch Continental shelf, comprises some fifteen developed fields located in six offshore production K/L Licence Blocks. The GIIP estimates for these fields range from 0.5 to 50 × 10 9 m3. Fields are linked to a network of production platforms and mini-satellites, and produce via a common export compressor into the WGT export line to Den-Helder. The gasfields are at varying stages of depletion, with some of the reservoirs now having been on production for up to 20 years. However, undrained volumes still exist, both as infill targets in existing fields, and as small to medium sized undeveloped structures at varying distances from existing infrastructure. Development of fields and prospects in the six Licence Blocks, jointly held between five Licence Holders, is governed by a Joint Operating Agreement, operated by NAM. All gas is sold under a single Gas Sales Agreement to Gasunie. These contractual arrangements allow an integrated development of all gas accumulations in the area. Execution of remaining exploration and development activities has significant impact on the performance of existing systems, and detailed planning is required to optimise total system performance. This paper describes the K/L Hi-cal gas system, and discusses the technical and contractual issues of the development planning and optimisation process employed for future development activities. A number of challenges are recognised in this development. Firstly, recovery from existing fields should be optimised. Secondly, making as much use as possible of existing infrastructure, recovery from newly discovered fields should be maximised. Finally, remaining exploration potential in the area should be realised, within the available window of opportunity presented by a maturing infrastructure. A brief description is given of the K/L Hi-cal gas evacuation and infrastructure, as well as of the contractual arrangements governing the Licence area. Next, the gas field planning tool employed in NAM for evaluation of gas field projects is discussed, followed by an analysis of the main issues in the development, and strategy to resolve these issues. Finally, it is shown how exploration activity in the area is integrated with the development effort. P. 575^