Abstract: In the North Tluwa Oilfield at the east margin of the Pre-Caspian Basin, the complex carbonate reservoirs are commonly characterized by complicated geological structure, variable boundary and thickness of target layers, and low ROP in lower highly-abrasive lime mudstone. In addition, for achieving higher production per well, the horizontal section of a horizontal well has been increased from 400 m to 1000 m, which brings great challenges to the control over borehole trajectory and quality. To cope with the challenges, integration and application of drilling technologies in a long horizontal-section well were carried out, and the optimized and fast drilling technology involving the rotary steerable drilling system, the Stinger bit and the PeriScope system was developed. This technology was firstly applied in Well H814 in the North Tluwa Oilfield with good results. Specifically, the rotary steerable drilling system made it possible for rotary drilling in the target layer and reduced drilling risks, the stinger bit realized a ROP more than doubled, and the PeriScope system provided precise localization of pay zones and improved the reservoir-encountered rate from 55% to 83.9%. The optimized and fast drilling technology can be promoted to other oilfields in the Pre-Caspian Basin where the strata are developed regularly.

Key words: complex reservoirs, highly-abrasive formation, long horizontal section, optimized and fast drilling technology, rotary steerable drilling system, Stinger bit, PeriScope, reservoir-encountered rate