Pushing-up Field Ultimate Recovery to Top Quartile through Infill Development - A Case Study of a Carbonate Waterflood Field

摘要

PDO has a diverse portfolio of mature fields undergoing waterflood. These fields open-up an additional opportunity through infill drilling for enhancing the ultimate oil recovery. It has been established in the oil industry that increased well density does not only result in acceleration but will also lead to incremental recovery. This paper demonstrates the approach taken for identifying and maturing an infill development in a Shuaiba matrix carbonate reservoir within a thin oil column. The case study field has been developed predominantly with single long (~ 1.5 km) horizontal oil producers (lifted with ESPs) & water injectors in a Producer-Producer-Injector (PPI) pattern with a ~60 m spacing between Producer and Injector (P-I). The development team executed additional appraisal activities in parallel with implementing the field development plan. Seismic inversion was updated with the new well results which improved porosity prediction in un-drilled areas. Based on acoustic impedance guidance, appraisal wells have been drilled with encouraging indications in terms of producibility and opened new areas for further development. The history matched simulation model results showed that 120 m P-P-I spacing would recover 25% of in place volumes compared to 60 m P-P-I spacing with an ultimate recovery factor (URF) of 45%. The key success factors for the infill development are (1) well placement with geosteering, (2) balancing appraisal with development and (3) continually updating static and dynamic models. This is done to support development decisions such as well sequencing & placement, drilling activity and surface facilities expansion. The key learning from this case study is that developing fields initially with twice the proposed development spacing, nevertheless following the optimal water flood pattern, is the best way for appraising the whole field rapidly. This allows time to gather much needed information ahead of making tactical investment decisions on long lead-time surface facilities. The case study field development & maturation activities enabled pushing-up the ultimate recovery above 33%, bettering the top quartile recovery factor and achieving a sustained oil production forecast of above 20,000 units for the forthcoming 6+ years. The methodology developed and presented in this paper could be adopted for typical water flood developments.