Well Control Experiments related to Slim Hole Drilling

Well Control Experiments related to Slim Hole Drilling. Abstract During June 1994 slim hole well control experiments were performed in an inclined onshore research well in Stavanger, Norway. The tests were gas kick, annular pressure loss and surge/swab experiments. A total number of 36 kicks were performed during these experiments. In addition we did flow tests circulating the well at various flow rates with and without rotation. The pressure loss effects of rotation on flow were logged. Tests in both plain drilling water and muds were done. Surge and swab pressures were logged downhole when reciprocating drill pipe at various tripping speeds. Raw data files containing approx. 110 Mbytes in ASCII files of downhole pressure data, and surface data have been gathered for further analysis. The data was of high quality and provide opportunities to improve existing well control procedures and to incorporate this knowledge into future drilling operations. This paper summarises the experimental conditions during which data were recorded, main results and some operational recommendations. Experimental parameters such as influx type (liquid/gas), gas concentration, kick injection rate, mud flow rate, drillstring rotation rate, pipe reciprocation etc. were varied. Three kick detection systems and one flow meter were tested during the experiments. Introduction Well control is very critical during slim hole drilling, due to the importance of the annulus pressure loss as well as the small mud volume in the well. Operations like pipe rotation, reciprocation, tripping etc. may generate high transient pressures in the well. Unwanted influxes and fractures may be initiated also. The effect of rotation on the frictional pressure loss in an annulus has been studied experimentally. Well control and hydraulics have been studied experimentally in full scale previously. An experimental programme for studying annular pressure losses and surge-swab pressures in oil based muds has been performed. Full scale kick experiments in both OBM and WBM in an inclined research well have also been reported. Experiments to validate kick control and pressure loss predictions have been performed in a slim hole test well. Tests related to continuous coring has also been reported. A number of well control issues for slim hole drilling have been studied experimentally in a full scale research well. The well, which is 2020 m long with 63 deviation, was heavily instrumented both on surface and downhole. P. 101