This paper discusses the further development of Burhaan West Field, a complex multilayered onshore tight gas reservoir that is one of the largest in the Sultanate of Oman. After several years of production through vertical comingled fractured wells, the foreseen decline below production target triggered an integrated assessment of the field. After considering various subsurface development and surface evacuation options, an opportunity for further field development at minimum cost was identified and selected. The integrated assessment of the field for further development optimization included the following work-streams:
Interdisciplinary data analysis to determine the critical elements of the recovery process.
Building a range of integrated models capturing the subsurface complexity and diversity of rock properties.
Optimized well type and spacing which focused on the advantages of infill drilling for improved aerial/vertical drainage.
Phased development along with de-risking of the newly proposed areas.
Decision based integrated production modelling to screen various evacuation options.
The development of a Well Reservoir and Facility Management (WRFM) strategy.
The proposed optimized field development enhances the field gas production capacity by 50%, while increasing ultimate recovery by 24%. This is achieved at low surface development cost, utilizing existing facilities, through infill drilling in the Core area and development of the Extension area. The conducted work highlighted the following key aspects of developing a tight gas reservoir:
Integrated cross-discipline data analysis is required to identify the critical elements contributing to gas and condensate recovery processes. In the Burhaan Field, this has revealed the presence of key marginally resolvable to sub-seismic features that were not previously identified.
Integrated Assessment (Integrated Production Modelling) enables for robust and quick evaluation of a variety of surface development options (e.g. evacuation routes and capacity) that is a key in achieving significant project cost optimization.
Large gas field developments generally benefit from a phased development approach, where newly proposed areas can be de-risked while high confidence areas are being developed.
A comprehensive WRFM plan is a key component of field development. This plan focuses on the activities required to address the field specific uncertainties and associated risks. It needs to be strictly implemented to ensure the delivery of promised volumes.
This case study shares the insights on the challenges faced in developing multi-layered tight gas fields. It highlights how development decisions need to be governed by field specific characteristics that can be identified through multi-disciplinary integrated data analysis. The paper also provides an example of an effective Production Modelling workflow to screen through surface development options and demonstrates how focused data acquisition and specific WRFM activities can be embedded into tight gas developments.