Study On Distribution Of Residual Oil In Sandstone Reservoir Of Maozhou Oilfield

Complex fault block reservoirs account for a large proportion of onshore oilfields in China.With the water-cut creasing,the oil production shows a decreasing trend at the middle/ late development stage.Due to its characteristics of small blocks and large faults,there is still a lot of residual oil remaining in the formations.Maozhou sandstone reservoir,which has been developed for 30 years,is a typical complex fault block reservoir.Some blocks are at "double high" development stage with high water cut and high degree of reserve recovery.Many factors result in its poor development,such as low permeability,strong heterogeneity,prominent contradiction between injection and production,many low efficiency or shut-in wells,etc.Therefore,fine geological modeling,systematical reservoir characteristics and residual oil potential should be studied.I made a plenty of investigation in relevant literature both at home and abroad and research achievements of Maozhou Oilfield in recent years in order to raise the level of understanding.On the basis of understanding geological features and development of the block mo32 and the block mo34,digitize interpretation results of microfacies and establish the structural model,phase model and the attribute model controlled by Phase control constraint.Then numerical simulation of reservoir is made to modify the geological parameters.The plane and vertical distribution characteristics of the oil sand bodies in each layer of main target formations are confirmed.Affecting factors and types of residual oil distribution are found out.The scale of residual oil are quantified.The results show that the residual oil is mainly distributed in following areas,such as unexploited reservoirs,oil-bearing sands with unformed injection-production,pinch-out areas nearby.Besides,the imperfect water flooding areas,resident oil areas,dispersive residual oil areas after water flooding also exist a lot of residual oil.It is considered that residual oil which is affected by inter-layer interference can be produced by stratified water flooding,residual oil in low permeability and ultra-low permeability reservoir can be produced by fracturing and residual oil in the unused oil layer can be produced by reperforated.Besides,adjustment wells drilling also can increase the degree of reserve recovery.Production adjustment program designs are completed and corresponding numerical simulations and development index predictions are made,which provided a direction in reservoir development next step.