Study On Recovery Of Water - Driven Gas Reservoir

The study of water drive gas reservoir recovery is an important content of making and adjusting development program, but the existing methods of determining water drive gas reservoir recovery at the early development are mostly based on the field development experience, lack of theoretical basis.In this paper, on the basis of a large number of literature investigation and previous studies, the theoretical calculation method for water drive gas reservoir recovery, the corresponding calculation software and its main influence factors are studied, and an application example is given. The main work and the achieved conclusion and understandings are as follows:(1) The principle, steps, advantages and disadvantages of various early identification methods for water influx of water drive gas reservoir are analyzed, and the determination methods of water production type and its output law for water drive gas reservoir are summarized.(2) Based on the study of the material balance equation, water influx calculation model and endpoint equation for water drive gas reservoir, the unitary processing for Agarwal equations is carried out and then the method to determine the water drive gas reservoir recovery is improved, and the corresponding calculation software is compiled with MATLAB7.1, thus calculating gas reservoir recovery rapidly and easily when the parameters take different values.(3) By applying the improved calculation method and software of water drive gas reservoir recovery, quantitatively analyzes the influence way and influence degree of the six main influence factors affecting on water drive gas reservoir recovery, respectively. Comparing the curve shapes and trends of the calculated theoretical instruction curves with previous theoretical curve chart, find that the latter is difficult to reflect all curve shapes and trends of the former.(4) Supplement and perfect the method of calculating the average formation pressure of gas reservoir with the gas well head pressure data. On the basis of analyzing the traditional water influx calculation method and simple method, the method is established to determine the aquifer size of gas reservoir.(5) The average formation pressure and aquifer size of Y1I north gas reservoir of LD22-1gas field are calculated. The theoretical instruction curve calculated by the improved method and software match the actual data of Y1I north gas reservoir very well, which prove that the calculation method is practical. The recovery of Y1I north gas reservoir under the conditions of different ultimate volumetric sweep efficiency and different gas production speed respectively are calculated with the compiled software, and the results show that increasing the ultimate volumetric sweep efficiency and gas production speed can improve the Y1I north gas reservoir recovery to a certain extent.Through the above research work, the paper develops a system method which from identifying water influx and calculating formation pressure, aquifer size and water influx to calculating recovery and quantitatively analyzing the influence way and influence degree of the main influence factors affecting on water drive gas reservoir recovery, providing the determination of water drive gas reservoir recovery and reasonable development plan with a new theoretical basis.