Considering that light-capacity hoists have found wide application in TATNEFT during well interventions and due to growing number of wells equipped with packer and anchor assemblies for artificial lift operations, conventional well intervention tools may fail to facilitate unsetting and retrieval of such equipment. This prompted engineers of TatNIPIneft Institute to develop DUG-40  wellhead hydraulic jack – a cost-effective solution to meet downhole challenges that does not require a workover rig. Currently available are various wellhead jacks. These primarily have large cross slabs and stand on the ground [2, 3]. Such devices are extremely heavy and require mobile cranes for mounting, particularly in cases of high-set tubing or stuck hanger. Such jacks also require special preparatory arrangements at the wellhead area (construction of a work site, laying support plates). The main unique characteristics of DUG-40 include travel length of as high as 1 meter, upward extension of upside-down cylinder, landing into production casing coupling, and clamping capabilities due to application of two spiders. Jack lifting capacity is 50 tonnes. The hydraulic jack has simple design; low-set top clamp ensures easy operation of the device. Due to landing into wellhead connector, the jack allows to detach stuck tubing head adapter (tubing hanger) from wellhead adapter flange. Hydraulic jack design provides for hydraulically forced return of the cylinder to its original position by utilizing the annular space between piston rod and the cylinder. Pilot tests of the hydraulic jack have been conducted in wells operated by TATNEFT Company. Various well intervention jobs have been conducted to gain the experience: unsetting of packers and anchors, stuck tools, tubing hanger. The paper describes hydraulic jack design and operation as well as field test results in 14 wells, which confirmed its efficiency.
wellhead hydraulic jack, cylinders, wellhead flange, wellhead connector, production string, top clamp, bottom clamp.