A Cable-Controlled Pressure Testing Technology for Separate-Layer Production

Abstract The separate-layer production system is usually used to solve the problems of low separate-layer control level, difficult water locating and plugging, high operation cost and low testing and adjusting efficiency. This paper proposes a cable-controlled pressure testing technology for separate-layer production. Through the interworking of adjustable production regulator, pressure measurement instrument, ground control host and fishing tool, the separate-layer pressure measuring can be realized. The pressure measurement instrument consists of releasing unit, two pressure sensors, electrical setting & releasing mechanism and control circuit. Due to the dimension restraint, the traditional mechanical releasing way is not suitable. Therefore, the electrical releasing unit is designed and the lead limit switch is applied to guarantee accurate releasing. The setting & releasing mechanism possesses double leather cups which adopts the combination of mechanical compressing and hydraulic dilating to improve the sealing reliability. Two independent pressure channels are employed for formation pressure and oil tube pressure, respectively. The pressure measurement instrument is run into the wellbore through annular by cable. When the meter is set with regulator, ground control host orders the controlling motor to release the meter. Then, on-board controlling circuit unpacks the leather cups to establish the pressure channel between individual formation and the pressure measurement instrument. After about 5 days, the pressure build-up curve of the formation can be achieved. The specialized fishing tool is run into the separate-layer production string to locate the pressure measurement instrument with the help of centralizer and guide mechanism. The releaser is captured with the fishing tool and the pressure measurement instrument is fished. In the oil immersion test, the leather cup showed excellent sealing in diesel oil under 50 Celsius degrees and 15MPa for 90 minutes. The measuring range of the pressure measurement instrument is 0-40MPa and the accuracy is 0.05%. The cable-controlled pressure testing technology realizes measuring of individual layer and is characterized by high accuracy, small diameter and fishing. During the testing, only the production of measured layers is suspended, with no influence on other layers. Field tests showed the maximum pressure difference of 2MPa between individual layer and full wellbore, which identified the necessity of separate-layer testing.