Using Managed Pressure Drilling Equipment to Troubleshoot Well Control Issues with Total Lost Circulation and Ballooning on A Semisubmersible Rig

Abstract

Abstract When drilling from a deepwater semisubmersible rig, the operator encountered wells problems, including lost circulation, influxes, and ballooning, in the 14 3/4-in. hole section. Managed Pressure Drilling (MPD) equipment that helped to mitigate these issues specifically, when stripping in the hole with the bottom hole assembly through the Rotating Control Device (RCD) bearing assembly while managing surge and swab pressures, monitoring the well while displacing heavy mud into the open hole, conditioning the contaminated mud, removing gas from the well, and fingerprinting the flow back to verify ballooning against influxes, and finally stripping out of the hole. The operator experienced a total loss of circulation at the 16-in. liner shoe at 1,633m while drilling the 14 3/4-in. hole section. Several lost-circulation material (LCM) pills of different weights were pumped to cure the losses without success. Then the well was flow-checked, the gain was noted, and the well shut-in. Having the MPD chokes and the Coriolis flowmeter in place made it possible to adjust the surface back pressure (SBP) accordingly within a small operating window. As a result, the operator could achieve the key objectives of stripping the drillstring in the hole, stripping out of the hole, and rolling over to spot 1.88SG heavy mud on the bottom using the pump and pull method. After LCM was pumped and a hesitation squeeze performed, well operations were stabilized, and the casing was run to a 2,111m measured depth. Advanced flow monitoring enabled the MPD to determine the required SBP for balancing the well. MPD applied 60psi of SBP and noted a gain of 8.3bbl/hr from the flowmeter. Next, MPD applied 65psi SBP and the well was static. Then, MPD applied 70psi SBP, and the well took losses at a rate of 19bbl/hr. MPD allowed to successfully strip the BHA in the hole through the RCD bearing assembly to the shoe. Correct string displacement observed via the MPD Virtual Trip Tank, achieved by adjusting the SBP from 62psi to 125psi. The closed-loop circulating system enabled safely circulating and conditioning contaminated gas-cut mud in the hole back to homogeneous mud. MPD reduced SBP incrementally and fingerprinted flow back at every step to give assurance that well ballooning, and not influxes, caused the flow back. Dynamically adjusting SBP, coupled with advanced monitoring of the returns flow using the Coriolis flowmeter, enabled balancing the well despite the challenges of a mixed mud gradient in the annulus and a narrow operational window. The MPD riser consisted of an RCD below-tension-ring (BTR)-s, flow spool, and top and bottom crossovers. Rig modifications involved fabricating the fixed piping to allow integrating MPD equipment with the rig system.