Study On Production Capacity Evaluation And Rational Distribution Method Of Low Permeability Gas Reservoir In

Cai31wellblock gas reservoir is a typical gas reservoir with low permeability. Reservoirs are characterized by small reserves and high heterogeneity. It is very difficult to develop. Since the operation, the initial allocation is too high, which results in pressure and production declining rapidly. Currently, the wellhead pressure of gas well is similar to manifold pressure, which affects the normal production of single well. And Cai31wellblock gas reservoir lack formation pressure and well test data. Therefore, in view of above issues, in order to meet the requirements of stable production time, it is particularly important to research on deliverability evaluation method and reasonable production techniques for Cai31wellblock low permeability gas reservoir.Based on the literature research home and aboard, this paper synthetically used the theories and methods of many disciplines such as seepage mechanics, gas reservoir engineering, well test analysis, optimization algorithm and so on. Combined with the geologic and exploitation features of Cai31wellblock gas reservoir, this paper studied the following several subjects and got the corresponding research results:(1) The structure characteristics, sedimentary characteristics, reservoir properties and fluid characteristics of Cai31wellblock gas reservoir are analyzed and summarized. The production decline law, law of the pressure drop and water production characteristics of gas reservoir and single well are studied.(2) The conventional deliverability evaluation method is analyzed. Combined with abnormal data processing method, the initial deliverability of Cai31wellblock gas reservoir is evaluated by using the data of back pressure well testing and single-point method. The applicability of this method is studied. Most of the gas well have a long flow-instabled time and can not meet the request of time and production of the conventional deliverability testing, so the applicability of the conventional deliverability evaluation method in Cai31wellblock gas reservoir is poor.(3) The deliverability equation is separately deduced and established considering start-up pressure gradient and stress sensitivity. Combined with its material balance equation, the history matching objective functions of production and bottom hole flowing pressure are established by use of production data, and the dynamic deliverability evaluation method is established by use of multiple objective function optimum matching method. The deliverability effects of start-up pressure gradient and stress sensitivity of Cai31wellblock gas reservoir are studied, and single well deliverability of Cai31wellblock gas reservoir is evaluated.(4) For low permeability gas reservoir has a longer period of unsteady flow, the unsteady deliverability equation is deduced and established considering start-up pressure gradient. The unsteady dynamic deliverability evaluation method is established by using the same research ideas as the dynamic deliverability evaluation method. The unsteady deliverability effects of time and start-up pressure gradient are studied, and the single well deliverability of Cai31 wellblock gas reservoir is evaluated by use of the established method above. The results show that the history of matching better, and the calculated results close to the dynamic deliverability evaluation method, which describes the two methods are reliable.(5) Based on geology and development characteristics of Cai31wellblock gas reservoir, the model for calculating the dynamic reserves is established including the pressure drop method, the flow material balance method and the unstable production method. The single well controlled reserves of Cai31wellblock gas reservoir are calculated by use of the model.(6) Based on dynamic optimization allocation theory of constant volume enclosed dry gas reservoirs, the dynamic optimization allocation model of low permeability gas wells is established considering start-up1sressure gradient, carrying liquid, stable time, critical flow erosion production and so on. The effect of pressure gradient on the allocation is studied, and the initial reasonable allocation of Cai31wellblock gas reservoir is analyzed to give the initial reasonable allocation recommendations.(7) For the production stage of Cai31wellblock gas reservoir belongs to the later production stage, The piecewise matching dynamic allocation method is established considering start-up sressure gradient, carrying liquid, critical flow erosion production, stable time, transmission pressure, maximum production limit and so on. The method can maintain gas well continuous liquid-carrying and the years of stable production. It also can predict the formation pressure, bottom hole flowing pressure, production, and the recovery degree variation law with time. The effect of pressure gradient on the dynamic prediction is studied, and the current reasonable allocation of Cai31wellblock gas reservoir is analyzed to give the current reasonable allocation recommendations.