Application of Downhole Tractor in Gas Well Zonal Isolation

Abstract

In high angle wells, downhole tractors can be used for electric line (e-line) deployed toolstring conveyance. This paper presents the job design, planning, and execution of a rigless zonal isolation in a gas well located in the Gulf of Mexico. Downhole tractors were used as the method of conveyance during this zonal isolation. A deepwater direct vertical access gas well was suspected to have had a sand failure event. The well was assessed and identified to be a candidate for big-hole sidetrack (BHST). In preparation to the BHST, a zonal isolation was planned to be performed prior to the decomplete. This well is highly deviated with a maximum angle of 81.5 degrees. A downhole tractor was selected to be the method of conveyance for the required wireline operations. Due to well history, the wellbore was suspected to be obstructed by sand. Selection of mitigation methods to reduce the risk of sticking toolstring in sand fill is discussed. Methodology included the use of real-time video feedback to evaluate downhole condition, as well as the use of specific tension and release subs. Prior to execution System Integration Tests (SIT) were conducted between operator and service companies to ensure the e-line cable, tractors, and bottom hole assemblies (BHA) were fully compatible and operable. As part of the zonal isolation work, a downhole camera was deployed on tractor to observe the condition of the wellbore from SCSSV to proposed cut depth. A thru-tubing packer with blow-out plug was deployed on tractor and set on depth. A jet cutter was deployed on tractor and activated on depth. The zonal isolation job was completed without excessive tractor misruns. The job added significant value by reducing rig time needed for decomplete and accelerating well handover to Production. This case study demonstrates the capability of downhole tractor at deploying tools in a deep near-horizontal well, and downhole tractor’s compatibility with a variety of tools. Learnings relevant to the application of tractor conveyance are discussed.

Static Characteristics of Friction Block Teeth of Coiled Tubing Drilling Robot

“…Coiled tubing drilling technology is relatively mature at present, and it has the advantages of a short operation cycle [1], low pollution (small waste treatment volume), and cost saving [2]. When operating in a horizontal well, the coiled tubing cannot enter the well by its own gravity, and the tubing string in the well will be subjected to the axial friction of the well wall, causing problems of buckling and "locking up" [3], making it difficult to run the tubing string [4,5]. Some scholars have used mechanical drag reduction [6] and lubrication [7] to reduce the drag reduction to extend the length of the pipe string, but the total extension length is far from enough.…”

Control algorithm of weight on bit and rate of penetration based on drilling robot

“…However, the length of extension is extremely limited, and it cannot meet the development requirements of horizontal wells. 4 To solve this problem, at present, downhole robots are mainly used to tract the tubing into the horizontal well. [5][6][7] The downhole robot can provide axial traction force to overcome the frictional resistance, fundamentally solving the problem of the coiled tubing buckling and "locking up."…”

“…However, the length of extension is extremely limited, and it cannot meet the development requirements of horizontal wells. 4…”