Thermal EOR is one of the success stories in the fractured carbonate portfolio in Sultanate of Oman. This paper summaries the challenges, learning and best practices in executing field developments plans in one of the complex reservoirs in Oman.
In Thermally Assisted Gas-Oil Gravity Drainage (TA-GOGD), steam injected into the top of the reservoir to achieve two important phenomena: first to apply a gas gradient across matrix blocks so that the oil in the matrix drains down by gravity and secondly to heat up carbonate matrix blocks to initiates various mechanisms including solution gas drive, thermal expansion and viscosity reduction of oil to drain oil faster.
The selected field candidate is a fractured carbonate that structurally segmented into two distinctive blocks: Crest block and Sub-crest block which they contain of 25% and 75% of STOIP respectively. It has been produced with cold production mode over 40 years of heavy oil (~ 700 cp) and ultimate recovery 2% of initial STOIIP. This field shared a common aquifer with other nearby developed fields. This paper intended to discuss a suggested development plan for a combination of challenging environment including: the heavy nature of the oil, the fractured nature of the rock, the offtake fluids requirements and the pressure management given aquifer communication with nearby fields.
The development strategy of oil rim is driven by steam injection rate optimization into Carbonate field. Two strategies are designed: (i) full steam injection in crest and sub-crest blocks and (ii) phase steam injection (starting by crest block and then followed by sub-crest). The following conclusions can be drawn:
Aquifer communication impact the gross evacuation decision and lowering pressure strategy.
The reservoir simulation model can be used to optimize the oil rim management in the fractures.