Reservoir Characteristics Of Feixianguan Formation Gas Reservoir In Longgang Donglong Block And Optimization Of Favorable Area

For years of research into reef reservoir in north of Sichuan basin, a series of achievements have been made and operated significantly for local progressive development. This paper consists of sedimentology, organic geochemistry, reservoir geology, development geology, oil-gas geology and structural geology as background knowledge. Comprehensive compared, analyzed into adjacent drilling, logging, well logs data, then conducted studies like sequence stratigraphic division and comparison, oolitic-bank distribution characteristics, reservoir characteristics, reservoir control factors, favorable area optimization in Feixianguan Formation, Longgang East.Based on the upward shallowing cycle feature in study region, another similar stratigraphic division scheme and configuration have been set up in Feixianguan Formation. From this division scheme, Feixianguan was divided into5sedimentary cycles. At the same time, their corresponding sedimentary phases and several subfacies and microfacies had been achieved:open platform, restricted platform, evaporate platform, and trough-slope facies, of which platform-margin facies as favourable zone. For platform-margin facies, the second and the third cycles are oolitic-bank growth stages. Among these cycles, the second cycle has largest net pay thickness, best stabilization in horizon, strong dolomization and well developed formation.Within the study region, fracture-pore oolitic-bank facies is mainly developed. Main lithologies are oolite dolomite and sparry oolite dolomite rocks in which main are third class reservoir. Sedimentary facies, structural fracture and diagenesis are three key control factors on Feixianguan Formation. Prospecting oolitic-bank reservoir is mainly effected by the mixed water dolomization and burial dolomitization geological influence factors.Study suggested that, platform-margin belt is favorable accumulation area for oil and gas and trough-slope transition area is minor belt. Combined with the latest3D seismic outcomes, the favorable belt area has been calculated as334.61km2, sweet spot in3D oolitic-bank has212.96km2, and the most favorable area is around178km2. Gas reserve has in Longhuichang and Tieshannan oolitic-bank reservoir is obtained based on previous parameters and outcomes, which are27.216×108m3and46.79×108m3. Besides,18traps resources calculation within each typical gas reservoir are carried out, and their total area is133.77km, total indicated resources are325.43×108m3.