Well Test Analysis And Application Research Of The Multi-well Group In The Weibei Gas Field

Sebei gas field is the multilayer sandstone gas reservoir with complex hydrodynamic system and stronge anisotropy. In order to obtain dynamic parameters of the reservoir, and to estimate the interwell interference condition effectively, the well testing work of multiple well group —shut in the whole or most gas wells of a single layer to carry out pressure buildup testing, has been first to conducted in Seibei gas field. With the increasing number of the gas wells, it was found that the adjoining wells in a shut-in state has effect on the testing wells similarly in the testing process. However existing well testing models were single-well or two-well interference well testing models taking adjoining wells in a state of production into consideration without exception, the multi-well system well testing models considering adjoining wells in difference working cinditions are in short. Therefore if the existing theory and well interpretation method was applied into the interpretation of the test data in Sebei gas field, it could bring incorrect interpreted result and cognitive bias on the foemation. To solve the problems above, the study on the well test model of multilayered sandstone gas reservoir under the condition of the well testing for multiple well group should be carried out. On the basis of a large number of domestic and foreign literature research, the universal model considering the effect of adjoining wells on testing wells (working position of adjoining wells: wells open for production, wells shut in for testing, partial wells open for production meawhile partial wells shut in for testing) has been set up. Then on the basis of the universal model and combining the characteristic of actual gas field and features of the well test curves, three kinds of multilayered well test interpretation models under the condition multiple well group shut in have been eatablished:multilayer gas reservoir model without crossflow under the condition multiple well group, multilayer and two composite gas reservoir model without crossflow under the condition multiple well group, two layered gas reservoir model with crossflow under the condition multiple well group shut in. The sample curves were plotted and the sensitivity characteristics were analyzed combined the theory, main characteristics are: the number of layer, flow coefficient ratio between the layers, storage coefficient ratio between the layers, skin factor, mobility ratio, different composite radius and well spacing combination, rate ratio, well spacing, the number of adjoining wells. Furthermore the well test interpretation method suitable for Seibei gas field has been proposed and interwell interference judgment method under the condition of multiple well group shut-in. At last, the well test interpretation method has been applied to a typical layer group with multiple well group shut in to get the distribution of pressure, permeability, skin, gas water boundary and the closed-in time, which the more accurate interpretation results were acquired and the method was reliable.Through the study of this paper, a set of well test interpretation models under the condition multiple well group shut in have been built which provided theoretical idea and reference for the development in this kind of gas reservoir.