Key technologies of safe drilling in Zhongqiu 1 Well, a risk exploration well in Qiulitag tectonic belt

Well Zhongqiu 1 is located at No.1 Zhongqiu anticlinal structure in the middle section of the Qiulitage structural belt, the Kuqa depression, the Tarim Basin. It is a wildcat well deployed by PetroChina in 2017. In the Qiulitage structure, the surface conditions are extremely harsh, and underground structure is quite high and steep. Gypsum-salt layers are quite thick, subsalt layer, salt layer and suprasalt layer are structurally deformed. The seismic data is poor and the data of the neighboring wells is lack. The pressure coefficient of composite salt layer is complicated, and salt layer sticking is difficult. Drilling and geological design were studied precisely, construction scheme and risk control measures were optimized, and new drilling tools and drilling parameters were selected. Then, the countermeasures for well drilling, completion and ROP improvement in the Kuqa piedmont zone were formulated. That is to adopt the specifically tailored bit in the whole well and coordinate the well drilling, test and completion in subsalt layer, salt layer and target layer. Finally, different plugging measures were taken to deal with complex circulation loss in the low pressure zones of Suweiyi Formation and the composite salt layer interval of Kumugeliemu Group. After plugging operation was carried out by 14 times, the formation bearing pressure is increased greatly, and the drilling and completion cycle is shortened from 420 d to 350 d. The drilling practice of Well Zhongqiu 1 provides the reference for the oil and gas exploration and overall evaluation of Qiulitage structural belt.