Managed Pressure Drilling technology became popular and widespread in Western countries in the early 2000s and has long been successfully used for drilling complex wells onshore and offshore projects (for example in the North Sea, Gulf of Mexico and etc.) In Russia this technology has found its application relatively recently and still has never been used for offshore drilling. This article describes the results of the first MPD offshore application in Russia for drilling an HTHP exploration well in the Caspian Sea. A fully automated MPD set with early kick detection system (EKD) and back pressure pump (BPP) was applied, allowing to control pressure and drilling fluid outflow besides drilling, during connections. The drilling conducted using reduced mud weight in «near balanced» conditions, which compared to conventional strategy sufficiently reduced formation overbalance and losses risk as well. Specialized MPD tests used to determine formation and fracturing pressure limit in uncertainty geological conditions, optimizing core sampling drilling and mud roll-over strategy.

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Yurubcheno – Tokhomskoe oilfield is located in Eastern Siberia, Krasnoyarsk region, where the most part of oil and gas reserves are contained in Riphean high fractured carbonate reservoir. This reservoir contained a lot of secondary interstices and caverns, that are tend to enlarge due to excessive pressure exerted, that leads to loss circulation, differential sticking and associated NPT [1]. In case of conventional drilling on Yurubcheno – Tokhomskoe oilfield, such problems don't allow to reach the project depth in horizontal sections 152.5 mm (6in) – 1 000 m. The most popular method of struggling loss circulation is using loss circulation materials (LCM), which dramatically affects reservoir production properties. Furthermore, effectiveness of LCM wasn't enough, because volume of lost drilling fluid, which is oil based mud, remained too high. Managed Pressure Drilling technique was applied for resolving problems while drilling horizontal section in Yurubcheno – Tokhomskoe oilfield that allowed to reach the TD. Compare to conventionally drilled wells, using of MPD in Yurubcheno – Tokhomskoe oilfield resulted in reducing mud losses up to 3 – 5 times, reducing 152.4 mm section drilling time by 20% and increasing well production by 65 – 180%.

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The collaborative approach used for cementing the production liner in an onshore development well in Russia is presented. The reservoir has a narrow window between pore and fracture pressures, which has previously caused formation instability and severe lost circulation issues during well construction, compromising zonal isolation objectives. Total loss of fluids experienced while cementing the 114.3 mm production liner in the first appraisal well in the field led to revising the cementing strategy. Collaboration among various parts of the drilling department and the opportunity to define a new approach resulted in a decision to introduce managed pressure drilling (MPD) to address the challenges associated with a narrow pressure window and uncertainty in pore pressure while drilling and cementing. This enabled implementing the optimal mud weight and adjusting equivalent circulating density (ECD) during cementing with minimum overbalance. Reducing the mud weight from 1.20 SG to 1.05 SG eliminated losses after running the liner and while cementing it. As a result, pre-job circulation rates and pumping rates during cementing could be increased, improving mud removal efficiency and achieving top of cement at the required depth. The constant-bottomhole-pressure mode of MPD was used to maintain the same ECD during displacement of the well to a lighter fluid and during cementing, avoiding well influx during pumpoff events by compensating for the annular friction pressure loss with surface backpressure. This first onshore managed pressure cementing operation executed within the same field in Russia (later named as field A) was completed flawlessly, with no safety or quality issues, zero nonproductive time, and achievement of the required zonal isolation across the challenging production section. The collaborative approach used was a novel strategy, with the mud weight program strategically adjusted before and during the cementing operation to achieve zonal isolation objectives.