Analysis And Application Numerical Welltest Analysis In Gas Wells

During the practical process of oil and gas field development, conditions like the anisotropy of the reservoir, the complex boundaries and the multi-flows are becoming more and more. It is shown in the study that satisfactory results about these complex welltest problems can not be obtained by using the analytical method. However, we can use the numerical method to develop mathematical models fitting for any reservoir characteristics and flow regular patterns, and compute the model by numerical method. Then, the influences of many factors on well test curves can be considered. The results show that welltest problems, which can not be resolved by using analytical method, are resolved by using numerical method, and the welltest theories are enriched and developed. A new and effective method for the interpretation of testing data in complex geology and multi-flow conditions is presented. Therefore, the studies in this paper are as follows:1. The mathematical model of single phase flow and gas-water flow is developed and solved by using finite element method.2. The wellbore storage coefficient and skin factor are introduced by using Laplace Transformation and numerical inversion, and the numerical welltest theory curves of gas wells are plotted. Based on the characteristic of gas well in volcanic rock reservoirs, influences of the formation permeability, the anisotropy of the reservoir, the oil saturation, the fracture conductivity, the fracture length and the boundary property are analyzed.3. Numerical welltest method can contribute to the description of transient characteristic of complex gas reservoir. Thus the transient characteristic of complex gas reservoir is obvious, and it provides technical support for the formation description and gas reservoir development transient prediction.4. With the type curve match analysis, parameters like the formation permeability, the skin factor, the wellbore storage coefficient, the fracture length are obtained. The numerical results are contrasted with the conventional welltest results. The parameters obtained by numerical welltest are close to the real formation parameters .5. By using the numerical welltest method to predict the productivity, the inaccuracy of productivity prediction is less than 20%, which further demonstrates the credibility of parameters obtained by numerical welltest interpretation.