Detailed Geological Modeling Of Inter-salt Sandstone Reservoirs

Inter-salt sandstone reservoirs are formed in the special geological environment. By multiple factors, these reservoirs are difficult to develop. Because of serious heterogeneity in these reservoirs, the interlayer and intrastratal contradiction is difficult, results in low recovery and great potentialities in later development. Analysis showed that the main reasons which restrict effective development with the inter-salt sandstone reservoirs are the special geological characteristics of oilfield.It is easy to form salt dome and steep stratigraphic in inter-salt reservoirs. The structure of reservoir is complex, which sandstone and mudstone usually are interbeded with salt rock. Sand body size of these reservoirs is smaller, which is lens in profile and imbricate in plane. In order to accurately predict residual oil reservoir and improve the development level of inter-salt sandstone reservoirs, it is necessary to establish a high precision of reservoir geologic model.While focusing on geological characteristics of inter-salt sandstone reserviors, this thesis, taking the reserior in the north area of Wangchang Oilfie for example, makes a detailed description of typical units of internal reservoir to establish a geological database of inter-salt sandstone reservoirs. While using the data of geology, seismic, logging, geology, core analysis and dynamic history etc. with a integrated analysis of seismic, logging, geology, numeric simulation and dynamic data, it builds a high-precision deterministic geological model. Whereafter, reservoir sandbody of the geological model is verified by static analysis. The numeric simulation technology with dynamic data is used to test the geological model built.According to the specificity of inter-salt sandstone reserviors, this thesis, using architecture-element analysis, makes a hierarchical description for Genetic sand.It results that there are three composite pattern in vertical, such as. superimposed contact, alluvial fill intercalation, distribution of isolation, and obvious zoning features in plane that channel sandbodies, river mouth bars, front blanket sand, predelta mud, and saline appeared in order. The relationship of sand body is complex for inter-salt sandstone reserviors which belong to the labyrinth reservoir. The abandoned river channel, top elevation difference, channel sand body size, and discontinuous sand body can be used as single channel. Single distributary channel can be used as a single of mouth bar to identify and partition causes sand body. Through the profile analysis for dense pattern, it determines the scale of various Genetic sand body, and the shape of sand body of north area in Wangchang Oilfield in plane with horse-shape, flower, flake distribution.Sandbody's thickness is small and its type has a significant effect on the development of inter-salt sandstone reservoirs. A study is made to built a reservevior mode on the level of genetic sand bodies. For the steeply structural features of north area in Wangchang Oilfield, this thesis, basing on the recognition of structural surfaces by advanced technologies, such as logging and seismic comprehensive method,ant tracking, time slices and so on., builds structure model by using double faults simulate salt dome structure. The architecture of inter-salt sandstone reservoir is very complex, and it is labyrinth reservoir. It takes salt layer, mudstone barrier as the independent simulated layer,and controled the sand body boundary of reservoir while structure modeling.Taking geological knowledge database,such as sedimentary model of inter-salt sandstone reservoirs,as the constraint conditions,it chooses marked point process simulation to build sedimentary facies model. For scattered distribution of sandstone, property effected by the salt ridge, strong heterogeneity in the inter-salt sandstone reservoir, it, under the control of structure model and sedimentary facies model,choosing Sequence Gauss simulation method, suitable to continuous variables, builds physical property model of reservoir by facies-controlling principles.It verifies the 3d geological sand body model from the lithology, profile correlation of the architectural structure model and the distribution characteristics of sand in plane. It gradually modifies 3-d geological model to achieve requirements of history matching according to reservoir numerical simulation. History matching results show a number of development indexes, such as field water cut, daily average oil production, cumulative oil production and so on, are highly consistency with the actual reservoir development curve. The matching rate about single well reached 78.6%, which shows the geological model accurately reflect the characteristics of internal reservoir.It is to prove the geological model by using the dynamic data. The dynamic responses show that geological model objectively reflects the actual geology.This paper try to find out a suitable reservoir modeling method for inter-salt sandstone reservoirs based on intercrossing of multi-subject and the integration of multi-technique. Based on lots of work, the modeling for such reservoirs should pay attention in four aspects:First, it should increase sand body studies in order to provide important geological knowledge base for modeling. This research will supply useful experiences for the later developing schedule adjustment of the north area in Wangchang Oilfield. The special technical means and methods in this work could help the similar reservoir modeling. Second,for the steeply structural features in this reservoir, it is necessary to build structure model by using double faults simulate salt dome structure, basing on the recognition of structural surfaces by logging and seismic comprehensive method,ant tracking, time slices and so on.. Third, it is necessary to build property model by combining facies-controlled modeling with sand control modeling and random simulation with deterministic model. Four, with the deepening of oilfield development, it should repeatedly verify the geological model by using the dynamic and static data and reservoir numerical simulation technology.