Optimized Pressure Transient Acquisitions Improve Development Planning of Tight Rich Gas Fields in Sultanate of Oman

Abstract

Abstract The main goal of this study is to evaluate the effectiveness of Pressure Transient Analysis (PTA) in tight condensate-rich gas fields in Sultanate of Oman. Initially, PTA was used to define the dynamic permeability, total skin factors, and assess impairment due to condensate banking around wellbores. However, after long periods of production, new objectives arose, including assessing impairment due to poor clean-up of fractures in depleted layers. The overall objective is to address PTA different signatures and complications and to use results to improve well and reservoir modeling for better field development planning and the hydrocarbon maturation process. To achieve the study's objectives, about 35 PTA acquisitions were conducted in four mature clastic gas fields in Oman, which include over 250 fractured wells and have been producing gas and condensate for more than 30 years. The study involved an extensive revision of PTA results to address the main issues of these fields. The researcher estimated most of the actual fracture dynamic parameters and compared them with the corresponding designed parameters. Also, PTA results have been utilized to fine-tune dynamic permeability models, improving the reservoir pressure history matching to give more reliable forecast and development plans. The study's results showed that proposed individual layer permeability models (controlled by PTA results) were much more reasonable, improving dynamic modeling significantly. Delayed hook-up of fractured wells led to poor fractures clean-out in pressure depleted layers, resulting in weak fracture performance. The actual fracture parameters were much lower than expected before implementation, especially for pressure depleted reservoirs. By controlling the dynamic permeability model of each layer, using PTA results, condensate banking phenomenon has been simulated clearly, considering its negative effect on wells and field production performance. The researcher matched and proved the observed PTA results and prevailing responses (fracturing, condensate-banking) using sophisticated single and Box numerical simulation models. These models were incorporated into full field simulation models, leading to significant improvements in field production forecasts and field development planning.