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.
The closed chamber and tight hole methods of well testing described in this paper are designed to overcome some special drill stem test problems existingat the surface. The primary purpose for conducting this type of drill stem testis to utilize a system that offers maximum secrecy and/or maximum control of fluid recovery; therefore, maximum safety. The problem of secrecy commonly occurs in Canada, and the tight hole technique was developed so that only authorized personnel would be able to determine the type of recovery and the pressure involved. The closed chamber method has application wherever a high degree of controlof the recovery is desired, such as in townsite and night-time testing, neither of which can be accomplished safely by the conventional drill stem test method.This method also permits a high degree of safety when testing high-pressure gassands. Experience with closed chamber testing has indicated that the fluid recovery data may be applicable for empirical analysis to determine reservoir fluid properties provided that certain problems are recognized. Static reservoir pressure can be determined by employing the initial shut-in-flow-period method described in the text of the paper. However, problems are encountered when attempting to utilize the pressure buildup curveto determine transmissibility and permeability with the degree of accuracy obtainable from a conventional drill stem test. Examples of pressure curves from tight hole and closed chamber systems are included and discussed. Introduction Tight hole testing was developed to provide maximum secrecy of drill stem test results in Canada. In order to maximize secrecy, it was necessary to provide a testing system that would not allow fluid recovery to be exposed to unauthorized personnel on or off the rig floor. The tight hole assembly consists of a closed chamber which allows the standsof drill pipe forming the chamber to be separated, drained and set aside in the derrick without revealing any recovery, even in the tool joints, to unauthorized personnel. Secrecy requires the elimination of surface indications during the test and the bringing of the recovery to the surface in such a manner that it will not flow freely from tool joints onto the floor or into the derrick. The recovery has to be removed from the chamber with maximum controlin order to provide secrecy. The conditions required for secrecy result in an increase in the safety of testing.
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