Research and Application of Compound Plugging Removal Technology in HTHP Condensate Gas Well
Authors: Wu Hongjun , Huang Kun , Liu Ju , Zhang Bao , Liu Jiquan , Kong Change , Shen Jianxin , Chen Lan , Tang Shenglan , Chen Defei , Tu Zhixiong , Li Zhen 
Published: March 2021

Dabei and Dina 2 gas fields located in Tarim Oilfield are HTHP and high production condensate gas fields. The formation temperature is 136°C, the formation pressure is 105MPa, the gas production of single well is 40×104m3/d~100×104m3/d, and the condensate production is 35t/d~86t/d. After the HTHP condensate gas well started production, the oil production pressure continues to fluctuate and decline due to the wellbore plugging. By 2019, more than 80% of the HTHP condensate gas wells have the wellbore plugging problem, gas production of some wells reduced over 50%, a few wells even shut in, the normal production of condensate gas well is seriously affected.

In some condensate gas wells of Dabei gas field, organic plugging substances are obtained in the wellhead and the nearby oil pipes during the well passing and other operations. Wax is detected and analyzed as the plugging substance. In addition, inorganic plugging substances are obtained at the bottom of the production pipe in the wells with serious plugging, through the coiled tubing dredging and overhaul operations, which are mainly concentrated at the reducing tool or screen pipe. The content of inorganic scale in the plug is 60% ~ 90%, and the rest is a small amount of formation sand.

In view of the problem of wax deposition on the upper part of the wellbore and plugging the tubing of the condensate gas well, the condensate oil samples and wellbore wax samples were obtained on site. The experiment analysis confirmed that the condensate oil dewax temperature is 37.1°C, which can provide a reference for judging whether the wellbore had wax deposition. In order to solve the problem of wax deposition in the wellbore, the laboratory evaluation experiment of wax remover optimization was carried out to optimize the wax remover with good wax dissolving effect. In view of the inorganic scale plugging at the lower part of the wellbore, the research on the scaling mechanism of high-pressure well bore was clarified, and the high dissolution and low corrosion solution acid system was optimized through the laboratory experiment.

For the wells with wax deposition and scale compound blockage, but have flow channel, a compound plugging removal technology is formed, which is to inject wax remover to remove the wax plug in the upper part of the well, and then inject acid system to remove the scale plug in the lower part of the well. For the wells with serious well plugging, a compound plugging removal technology is formed, which is to dredge the well through coiled tubing to form a flow channel, and then inject acid solution to remove the scale plug in the lower part of the well. Three wells have successfully implemented wax and scale compound plug removal, and the average single well productivity after plug removal is 2.7 times of that before plug removal, At present, the production of DB2-A Well has been stable for 22 months after plug removal. three wells have successfully implemented "coiled tubing dredging + wellbore acid plugging removal" complex plug removal, and the production capacity has been successfully restored after operation, the average single well tubing pressure is 60.4MPa, and the total daily natural gas production is 178×104m3/d. HTHP condensate gas well wellbore compound plug removal technology can remove the organic and inorganic plugging in the wellbore to the high efficiency recovery of the well.