Application of low-frequency electromagnetic wireless transmission test technology in the complex fault block reservoirs of Abei sag

Abei sag is structurally complex and its hydrocarbon accumulation laws are not understood clearly, so the conventional test technologies fail to read bottom hole shut in or downhole data in real time, which makes it difficult to control data accuracy and shut in time. To this end, the low-frequency electromagnetic wireless transmission test technology was optimized and the existing problems were corrected so as to enhance the pertinence and reliability of test data. To deal with the unsuccessful downhole signal docking, the short-circuit position in the string structure was analyzed, and the test tool and the string structure were improved. The inner diameter (ID) of the metal shaft of the centralizer was increased from 76 mm to 80 mm, the metal centralizer at the topmost was replaced with a nylon centralizer, and the outer diameter (OD) of the body of the positioning sub was decreased from 102 mm to 62 mm. To solve the problems of weak electromagnetic signal and short transmission distance, the design of the signal amplifying line was optimized and the research of weak signal detection technology was enhanced. As a result, the downhole long-distance transmission of 40 m is realized. What’s more, the transmission structure of the signal receiver was modified to transform the single-point reception into the two-way reception of communication loop. This technology has been applied on site in Well X16 of Xinsumu structural belt. Perforation-well startup-shut in process and test curve radial flow data are monitored in real time, which ensures test success rate and well test result effectively and provides technical support for the following exploration deployment in Abei sag.