| Popis: |
While drilling well in the Pre-Caspian basin, a presumably technogenic nature zone of influx was exposed, which did not fit into the model of the geological structure of the section. Attempts of influx management were unsuccessful. The well had to be abandoned without reaching the target. This article describes the experience of Managed Pressure Drilling and Cementing technologies deployment, process features and equipment hookup in unconventional wellhead configuration and Slim Drill type of rig. Application of MPD technology made reaching target depth successful in the condition of constant water influx. Drilling proceeded in complicated geological conditions: simultaneous crossflow between influx and losses zones, as well as drilling mud gradual replacement by formation fluid. Bottomhole pressure was controlled by Surface Back Pressure made by MPD choke and sealed wellhead using a Rotary Control Device (RCD). The compact set of MPD equipment was rigged up as ergonomically as possible due to space restriction of slim hole drilling techniques. The MPD technology made it possible to complete the construction of the section without curing losses and weighting the drilling fluid up to control technogenic influx, safely and effectively control bottomhole pressure and achieve geological targets. MPD tests were performed at various depths to determine formation pressure and formation integrity, which made it possible to determine the drilling window for successful construction of the section. After finishing drilling, a pull out of hole and well logging was carried out in an open hole on a drilling pipe with pressure control, which was previously impossible due to the high intensity of influx. Running 4-1/2" (114 mm) casing with pressure control, as well as cementing in MPC mode were applied. The surface backpressure was gradually reduced during cementing as heavy cement was pumped to minimize the risk of cement loss while controlling formation fluid influx. As a result, cement was lifted through the annulus to the wellhead, which finally eliminate the complication associated with the presence of incompatible zones of loss and influx, and to eliminate behind-the-casing flows. The economic feasibility of well construction was maintained by set of equipment adapted to non-standard conditions The first application of MPD technology on the Slim Drill (small-sized drilling rig) project successfully revitalized previously abandoned well. It shows the validity of using MPD technology by the help of optimized set of equipment. The work reveals broad prospects for replication on a previously inaccessible wells due to economic reasons. |
