Technology of prevention leak while drilling for leaky formation in Liujiagou Formation in Dongsheng Gas Field

Abstract:

Circulation loss in Liujiagou formation in Dongsheng Gas Field occurs frequently with large leakage amount and low treatment efficiency， resulting in long drilling periods. With geological data， logging data and electron microscope scanning， the fracture width of Liujiagou Formation was analyzed to determine the mechanism of fracture type leakage. The leakage data of Liujiagou Formation was summarized， the prediction model of leakage pressure was established through data fitting with the help of the correlation between leakage rate and differential pressure， and the transverse distribution profile of leakage pressure in Dongsheng Gas Field was drawn so as to provide quantitative basis for the optimization of circulation loss prevention technology. The calculation model of circulating pressure consumption and induced pressure is used to develop the wellbore pressure prediction method， and the influence laws of pumping rate， drilling speed， tripping-down speed and drilling fluid properties on wellbore pressure were analyzed to optimize drilling parameters. Rigid particles， fiber materials and sheet deformation materials were selected with optimized particle size gradation and component make-up ratio to develop the pre-pressure plugging-while-drilling system which provided. sand bed pressure bearing capacity exceeding 7MPa. Field application showed that the circulation loss in horizontal wells was reduced from 57% to 25.7%， the average circulation loss per well was reduced by 80.6%， the average leakage times per well was reduced by 88.1%， shortening the drilling periods.

Key words:lost circulation;induced fracture;leakage pressure;wellbore pressure;circulation loss prevention while drilling;Liujiagou Formation;Dongsheng Gas Field