Research And Application Of Steady State Instead Of Transient State Method

The reservoir geological situation is described by all kinds of geological parameters such as porosity, water saturation, permeability, production layer thickness and so on. Of all these parameters, the permeability inside the control range of the gas well is the most important and difficult parameter to determine. There are two methods to determine the permeability. First, the permeability could be determined by well log interpretation or core test, but it only stands for the very small area of the gas well. Because the carbonate rock is brittle, the core could easily produce micro-fracture since the pressure was released when it was brought out from well. Since the alternation is irreversible,errors will be produced even if the test is taken under the underground situation,so the permeability result taken by core test is not reliable. The second way is through well test interpretation. But the well test interpretation needs to shut down the wells to get test data, especially for some low-permeable and super low-permeable reservoirs, the shut-down time is much longer. The shut-dowm operation might interfere with the gas field production.In order to get more accurate permeability in the control range of the gas well,the author has proceeded further research about the method of steady state instead of transient state on the basis of previous research,and have got good results in practical application.It is quite important to get as much data as possible and make the best use of the data.The methods above either have some defects. On the basis of elastic drive theory, Carl proposed Steady State Instead of Transient State Method to approximately resolve unstable seepage flow problems.Because permeability is difficult to determine,the method is mostly used for theoretical analysis but hardly could be put into practice. The paper made further study on the basis of this method, and made it a well–control range permeability calculation method by using current daily production data.The main conclusions are:1. The author has proceeded further research of this method and used it to resolve some field problems in Shapingchang and Wubaiti gas reservoir. Also it is proved that this method was practical in this application.2. By reciprocal contrast with well test analysis and other methods, it has been proved this method had a relatively perfect effect in dynamic evaluation of the reservoir.3. Reasonable explanation and resolution has been proposed to the problems in applying the method.4. Through using the method of steady state instead of transient state in two gas fileds, the paper summarized and analyzed bother the advantages and disadvantages of the method to provide advice for the future applications of the method.