On February 7, Henan Oilfield reported that the second open casing of the Zhao X well, which was supported by the Academy of Engineering with core products, development of high-calcium drilling fluid system and technical support for field application, was successfully lowered to the design depth, making the first application of high-calcium drilling fluid system in Henan Oilfield a success.

The mud shale formation in the Uyang depression block in the Nanxiang basin of Henan Oilfield is prone to problems such as hydration swelling and spalling off blocks during drilling construction, resulting in downhole complications such as well wall instability, stuck drilling and blocked electrical logging, which seriously affects well safety and drilling cycles. In order to solve the important and difficult problems in the drilling construction of this block, the Institute of Drilling Fluids, the Shelfoil Company and the Henan Oilfield Engineering Institute formed a technical team integrating "research, production and use", and on the basis of full research and analysis of the geological characteristics of the area and the data of the neighboring wells, developed a technical plan for a high-calcium drilling fluid system with good inhibition and anti-pollution ability. The technical solution was developed based on the geological characteristics of the area and the data of the neighbouring wells. Through repeated indoor tests, the formula of the high-calcium drilling fluid system with SMPFL-C, a high-temperature anti-calcium polymeric filter loss reducing agent, as the core treatment agent, was optimized, and the construction plan on site was improved.

The successful application of this well proved the technical superiority of the high-calcium drilling fluid system for drilling and construction of mud shale formations, demonstrated the advantages of the Engineering Institute in drilling fluid systems and high-end treating agents, and also provided a reliable technical solution for drilling and construction of mud shale sections in the Zhaoou Block and other blocks in Henan Oilfield, providing strong support for the high-quality development of Henan Oilfield.