Experiment And Application Of Intake Flow In Directional Gas Well

Slant wells can increase contacted areas between wellbore and gas reservoirs, improve the gas production, reduce operating cost, it has become a key technology for low-permeability gas reservoirs at home and abroad. Once there are loading liquids in the wellbore, it would seriously affecting the gas rate, and even lead to shut-in. It is because we cannot recognize two-phase pipe flow mechanism in the kick off section, and unable to get the laws of liquid unloading and loading. If using conventional unloading-liquid model to predict slant well’s critical gas-flow rate, it will be very different. Therefore, this paper have developed simulation experiment device including vertical section and inclined section, and have studied on phenomenon of droplet formation, deformation and crushing process in the simulation wellbore. There is also studying the effect of pressure and temperature by the well course, establishing a critical velocity method of slant wells, forming the comprehensive theory and methods of predicting the critical velocity. The result of research has important theoretical and practical significance in the gas reservoir and gas condensate reservoir. In view of the above questions, this paper is based on the critical velocity theory, combined of theoretical analysis and physical experiment, this paper mainly have carried out the following work:(l)We have established visualization simulation equipment, which combined by30x3mm plexiglass tubes. The inclined section angle in the experiment device can be arbitrarily change, we have simulated the process of unloading liquid in the gas well under different deviation angle, and also have observed phenomenon of the liquid fall and accumulation, and test relative parameters of the curve when it is critical condition.(2)We carried out the critical velocity experiments under the three different inclination of20°,40°nd60°. Furthermore, we have evaluated the vertical section and inclined section tube critical both liquid gas model. At last, we amend the critical gas-flow velocity method of slant wells. And a result indicates:the critical velocity is greatly related with deviation angle. And with the increase of declination angle, it will first increases and then decreases, which is the result of the role of gas-liquid no-slip and droplet gravity.(3)It is based on the measured pressure data of Western Sichuan Gas Field, we divide the vertical section and slanted section, and adopting many methods of predicting pressure in order to statistics and estimate the pressure profile in the wellbore, forming a new combination model:when the production rate of vertical section was less than1x104m3/d, no slip model had a better performance, otherwise we use Hagedorn&Brown model, and DPI model was used in inclined section. We also adopt measured data in the Daniudi Gas Field to predict the new method, and a result indicates, the average error of the buttonhole pressure is less than2.12%, absolute average error is4.02%.(4)We established predicting temperature method, which was suitable for western Gas Fields, and adopting the nine times measure data to statistic and evaluate, the result show that the average error is1.95%, the absolute average error and standard deviation were less than5%, it is a good result.(5)We calculate the critical gas rate13times in the western Gas Fields and29times in the Daniudi Gas Fields, the result indicates that except seven wells’result is different from the judgment of tubing-casing pressure difference, other wells’result is consistent.