Study On Distribution Characteristics Of The Remaining Oil For Bottom Water Sandstone Reservoirs

Compared with the other reservoirs,bottom water reservoir has a certain particularity,such as the time without water is short,the water-cut is rising fast or the well is flooding when the wells start to product water,which make it difficult to be producted.Tazhong 4 Oilfield Donghe sandstone reservoir of Carboniferous is typical of massive sandstone reservoir with bottom water.The structure of the reservoir is a long axis of the anticline,the north wing of which is cutted by the 1 fault.The structure's long axis direction is northwest-southeast and the minor axis direction is cutted by a series of north-south trending approximately normal faults.Sedimentary material source direction mainly comes from northeast direction.Sedimentary facies is a shore beaches and tidal flat facies.Lithology of the reservoir is mainly light gray.gray fine sandstone,sandstone and glutenite are followed,the overall maturity structure of which is higher.The upper of the reservoir is heterogeneity,in which the interlayers are developed.The interlayer can effectively inhibit bottom water coning,the result of which is make a better development effect.Oilfield has been in the period of middle and late development stage,and the lower homogeneous formation has basically flooded,so the remaining oil'distribution is complex.This thesis takes Tazhong 4 Oilfield Donghe sandstone reservoir for example.Combined with the geologic characteristics of bottom water reservoir,interlayer developted and the product characteristics,the author study the affect of the interlayer to the remaining oil distribution and the characteristics and distributed model of the microscopic remaining oil.Basic on the theory,we integrate dynamic and static data and predict residual oil distribution using the softwars of modeling and simulation.At last,the develop recommendations are offered.Through the study,we obtain the results and recognize as follows:(1)By analyzing the influence of the geological factors such as faults,interlayers,micro-structure and other factors to the remaining oil distribution in the study area,we find that the interlayer plays a leading role on the distribution of the remaining oil.(2)Under conditions of the interlayer exist,the difference of the pressure between the top and bottom of the interlayer is the main physical condition in controlling the block of the interlayer.when the sum of displacement pressure of the interlayer and starting pressure of the fluid flow in low permeability reservoir is similar or equal to production pressure,the oil under the interlayer can flow up,at which the production pressure is the lowest pressure to allow the oil flow upwards,whereby we establish a formula of the lowest pressure and evaluate the the lowest pressure of Donghe sandstone reservoir is about 1.422MPa.(3)From the Water flooding experiments of the main pore structure,we consider that under the influence of exfoliation,dart,capture and separate action,the microscopic remaining oil distribution pattern of the mainly pore structure are plaque and half filling the hole type;the pore structure,driving direction drive mode are factors to the distribution of residual oil.(4)Through the numerical simulation,we find that macro remaining oil is mainly distribute in 1 to 3 layers,and scattered distribute in 4,5 and homogeneous segments formations,of which the movable remaining oil only exist in the local and closed at fault;the remaining oil of 1-3 small layer is focus on contiguous distribution in TZ401 block and the West Wing of the TZ422 blocks,the other parts of the study aera are high degree of flooding;injection-production imperfect,interlayer interference are the main project factors of macro remaining oil,interlayers and fault seal are the main geological factors of it.(5)Based on the theory and result of study,the author propose the measures to pruduct the potential remaining oil;compared with the base scheme,the new scheme can enhance oil recovery factor by 1.4 percentage points,which is feasible in study area.In the study of interlayer control remaining oil,the author combines the perspective of dynamics with fluid mechanics,and derives the formula of oil production,which makes the role of the interlayer better.This formula can provide the basis for determining reasonable production of the well in the similar reservoir.High-temperature and high-pressure micro-displacement experiments and coreflood experiments are made to study the mechanism,distribution model and characters of microscopic residual oil,from which we form a method which is suitable for studying the mechanism and distribution of high water contend.Through the above theoretical research,we formed a research ideas of remaining oil's distribution in the reservoir with high water content and big bottom water.The research ideas provide a theoretical basis for the development of similar reservoirs.Basic on the theory,we integrate dynamic and static data and predict residual oil distribution using the softwars of modeling and simulation,which is a foundation for reasonable recommendations to development.