Field A is one of the most challenging fields in the Potowar region of Northern Pakistan with severe problems of fluid loss, high-pressure shallow water influx, low drillability, clay reactivity/ shale instability and depleted reservoir sections. This paper gives a brief overview of the methods and changes made along with results achieved, enabling the well to reach total depth in just 31 days compared to an average of 150 days taken on offset wells.

Due to severe drilling challenges, the wells were drilled in six-hole sections starting with 36″ surface hole. An entirely new well engineering strategy has been utilized to enhance the drilling performance in the last five wells drilled in the field. Some of the major areas of change include Customized bit design, BHA and hydraulics design, casing design optimization and change in casing seat strategy as well as novel changes in drilling fluid design and selection of Loss Control Material.

Dysfunctions and limiters in drilling which were affecting the hole cleaning, mechanical specific energy (MSE), hydraulics efficiency, and ROP were eliminated.

A detailed analysis of the impact of changes in bits and bottom hole assembly design, drilling fluids design, and casing design is shared in the study for the last fifteen wells drilled in the field. Continuous learning and enhancements in all the subject areas are analyzed with respect to the use of different strategies and technologies. An analysis has been performed for non-productive time, its root cause and successful actions taken to reduce its occurrence. A huge reduction in drilling time, cost and risks have been achieved as a result of mentioned changes in the latest well setting a benchmark in the entire region. Dry hole time for the last well has been reduced by 78 %, while 65% cost reduction is achieved as compared to the previous average time and cost respectively. After removing the dysfunctions / limiters; ROP enhancement of 5 to 10 times has been achieved in different hole sections.

The learning and experience from the use of discussed technologies and drilling practices can be helpful for optimizing challenging wells with the problems of pressure reversals, drilling fluids losses, well control, drillability issues in gumbo clay/ shales and wellbore stability.

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