Streamline Numerical Welltesting Interpretation Method For Layered Reservoirs

By introducing the streamline method, a new numerical well-testing interpretation method is developed which can be applied to the actual reservoir geologic model and take many complex factors into consideration, such as production history, reservoir heterogeneity, well pattern, multi-phase flow, displacement mode, complex outer boundary conditions of the reservoir etc. And the multi-layer reservoirs are the focus throughout the paper. A series of streamline numerical well-testing interpretation models are presented for a variety of reservoirs with different geological and developing conditions, including both single-layer and multi-layer water flooding reservoirs, multi-layer polymer flooding reservoirs, reservoirs with complex near wellbore conditions as well as dual-porosity multi-layer reservoirs. The streamline numerical well-testing interpretation models mainly consist of two mathematical models, one for the production period and the other for the testing period. The former is actually a simplified black oil model while the latter is a streamline model composed of all the mathematical equations established for each streamline, which can reflect the influences of both the formation heterogeneity and different fluid properties, surrounding the testing well. Important advancements are achieved for streamline numerical well-testing interpretation models established for reservoirs from simple styles to complex ones, such as from single-layer to multi-layer, from water flooding to polymer flooding (considering viscosity of polymer solution, adsorption, permeability decline, inaccessible pore volume and other factors influencing polymer flooding), from single-porosity to dual-porosity, from simply common inner boundary conditions (entire perforation, wellbore storage effect, skin effect) to complex inner boundary conditions such as degree and location of the partial perforation, irregular contaminated zone etc., and it is therefore the well-testing interpretation models can fit the real reservoirs much better. The streamline method is selected to process and solve all the mathematical models, which shows the advantages of high calculation speed and reliable stability and thus set a good basis for the auto-matching interpretation of numerical well-testing data. The influences of many geological properties and well parameters on the pressure changes of a testing well are discussed and analyzed.A software for the streamline numerical well-testing interpretation is developed on platform of VC++, which makes a successful application of a newly proposed dual-population genetic algorithm and can be used to interpret a variety of parameters such as wellbore storage coefficient, skin factor, the distribution of permeability and remaining oil. The software is successfully applied in II3 layer of 437 block in Shuanghe oilfield in Henan with satisfying match between the interpretation results and the oilfield production data.