Unlocking the Potential of Complex Marginal Reservoir in Highly Mature Oil Field, XiJiang 24 South China Sea

An oil & gas operator in XiJiang block offshore South China has shifted the development of highly mature oil fields that have been producing for 17 years toward the remaining undeveloped marginal reservoirs using a horizontal well drilling program. The main targets of the new development campaign are the remaining thin oil column reserve in attic locations of the reservoirs as well as the unproduced thin laminated reservoirs in the area. Upon understanding the uncertainties and challenges associated with drilling horizontal wells in these complex reservoirs, an innovative drilling approach was initiated for accurate horizontal placement in thin sands, channel sands, and thin oil column reservoirs with strong bottom-water. The approach includes the integration of an advance multifunction formation evaluation Logging-While-Drilling (LWD) tool that provides real-time formation evaluation and structural interpretation along with a bed boundary mapper LWD tool with the ability to map multiple key boundaries that are the prerequisite parameters that must be identified during the execution stage and which include the water contact and top and bottom of the reservoir structure simultaneously in distance. Outstanding outcomes have been observed by implementing this new approach in the complex target reservoirs. The approach was applied to multiple challenging wells, each of which has produced from 2,000 to 6,000 BOPD with very low water cut, far exceeding the set production goals of 1,500 to 2,000 BOPD. These are very promising development economics in the oil fields that have 90% to 95% water cut on average.The successful implementation of the new development strategy in highly mature oil fields will lead to sustained and extended production, increasing the ultimate recovery and well economics. The approach provides an example of using integrated technology solutions to overcome the challenges in complex target reservoirs.