A Study On The Well Test Of Slanted Wells

At present, in the petroleum engineering field, oil and gas well testing, especially the transient well testing, is one of the most effective methods to obtain reservoir dynamics (systematic working dynamic of oil well), the results of which have irreplaceable effect on many fields such as reservoir evaluation, reservoir management, and reservoir description.With the improvement of drilling technique, the needs for developing multilayer reservoir, and some unfavorable geological locations encountered during the exploitation, multiple large angle slant wells have been drilled and well tested in Hailaer oilfield of Daqing oil area. But the study of dynamic analysis thoery and method about the slant wells falls behind. Now the downhole well testing technology and dynamic analysis method about the slant wells have not yet developed, seriouly affecting the high effiency applications of the slant wells. Based on the method of combination of theoretical analysis and field tests, the paper studies deeply the well testing technique and intepretation method of the well testing data about the problems existed in the slant well's well testing, and it has obtained the following resutls.(1) A set of well testing, fluid drainage and production test string about the slant wells is designed; and some downhole tools, such as, a new type of packer are studied. The well testing data quality of the slant well has been improved. All of which enhance the technological reserve for the enterprise, and fill the domestic gap in the field.(2) By establishing mathematical model of three dimensional steady seepage flow about the slant well, an accurate complex method and a simplified calculation method about the slant well skin factor have been obtained. The results show that when the well angleθ_w of the slant well is less than 75°, the calculation results of Cinco are more accurate; and whenθ_W is more than 75°, the results of Rogers are more accurate. These two methods can be used respectively according to different field conditions.(3) With the skin factor model, and the comparison with common straight well, non-dimensional increased production multiple is defined; and the quantitative calculation comparison indicates the main factor affecting the slant well's production increased ability. The results show that when the well angle is more than 60°, the production increase is significantly larger; and if the formation anisotropy is increased, the production increase is somehow decreased.(4) The mathematical model of transient well testing analysis about the slant well is derived; and a rapid and accurate calculation method is developed independently. In addition, the model is broadened from homogeneous anisotropic media to double-porosity media; some theoretical charts of related type curves are obtained; and the analysis of a single factor is completed. All of which solve the bigger error problem caused by approximately analyzing pressure data of slant well using straignt well model. The result is a new domestic achivement related to the research.(5) The well testing design flow is improved based on the results of the predecessor; and the well testing design method of slant well is established. The studies can be used to design well testing working system before the operation, and to optimize well open and shut-in time so as to acquire high quality pressure data and instruct the operation.(6) An evaluation method of transient productivity test for slant wells is newly established. When calculating the productivity, the productivity decline law of the reservoir is considered under the condition of slant well's three dimensional seepage flow, realizing the accurate evaluation of the reservoir productivity for the slant wells.(7) With the results of the paper, the author organizes and develops the practical dynamic analysis software of slant well. The software has three functions including well testing analysis, well testing design, and productivity evaluation. With the software, 13 slant wells (14 formations) are dynamically evaluated, attaining the goal of describing reservoir properties and understanding the productivity. The results can instruct the oilfield development in practically.