Drilling reservoir section in the oilfield located in Far North region is challenged with high risks of mud losses ranging from relatively minor losses to severe lost circulation. Numerous attempts to cure losses with traditional methods have been inefficient and unsuccessful. This paper describes implementation of Managed Pressure Drilling (MPD) and Managed Pressure Cementing (MPC) techniques to drill 6-1/8″ hole section, run and cement 5″ liner managing bottomhole pressure and overcoming wellbore construction challenges. Application of MPD technique enabled drilling 6-1/8″ hole section with statically underbalanced mud holding constant bottom hole pressure both in static and dynamic conditions. The drilling window uncertainty made it difficult to plan for the correct mud weight (MW) to drill the section. The MW and MPD design were chosen after risk assessment and based on the decisions from drilling operator. Coriolis flowmeter proved to be essential in deciphering minor losses and allowed quick response to changing conditions. Upon reaching target depth, the well was displaced to heavier mud in MPD mode prior to open hole logging and MPC. MPD techniques allowed the client to drill thru fractured formation without losses or gains in just a couple of days as compared to the months of drilling time the wells usually took to mitigate wellbore problems, such as total losses, kicks, differential sticking, etc. This job helped the client to save time and reduce well construction costs while optimizing drilling performance. Conventional cementing was not feasible in previous wells because of risks of losses, which were eliminated with MPC technique: bottomhole pressure (BHP) was kept below expected loss zones that provided necessary height of cement and a good barrier required to complete and produce the well. Successful zonal isolation applying MPC technique was confirmed by cement bond log and casing integrity test. Throughout the project, real-time data transmission was available to the client and engineering support team in town. This provided pro-active monitoring and real-time process optimization in response to wellbore changes. MPD techniques helped the client to drill the well in record time with the lowest possible mud weight consequently reducing mud requirements. The MPD system allowed obtaining pertinent reservoir data, such as pore pressure and fracture pressure gradients in uncertain geological conditions.

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.

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.

The utilization of managed pressure drilling (MPD) techniques has grown significantly over the past three years in the Russian Federation. This paper describes the application of MPD surface back pressure technique using both single and multiphase drilling fluid systems in several oil and gas fields located in Russia. The Komi Republic is one of the biggest oil and gas producing areas in the European part of Russia and among Russia's top ten producers. Although the Yurkharovskoye oil and gas condensate field in Western Siberia is in the Tazov Peninsula, most of the field is situated offshore. That part of the field is developed from onshore locations using horizontal and extended reach development wells. In Eastern Siberia, the Yurubcheno-Tokhomskoye field is one of the biggest oilfields and presents highly fractured carbonates. Each field presents a different challenge and requires a specific approach. The application of MPD technology improved drilling performance and helped avoiding non-productive time. Utilization of reduced mud weight with MPD procedures using a semi-automated system helped reduce lost circulation and safely control background gas, thus avoiding well control events in the Lambeyshorkoye, Komandirshorkoye, and Alabushina fields. In the Yurkharovskoye field, a high-pressure, high-temperature well was successfully drilled to TD with application of a fully-automated MPD system, which facilitated precise control of bottomhole pressure during drilling, pumps-off events, and tripping operations. A multiphase MPD technique helped achieve planned TD in horizontal sections in Riphean formations of the Yurubcheno-Tokhomskoye field without catastrophic fluid losses. By injecting oil-base mud with nitrogen, the equivalent circulating density (ECD) was drastically reduced, lowering the volume of losses up to 5 times. In addition, near balance conditions increased the ROP while drilling. The first ever multi-lateral well drilled with multiphase MPD was successfully completed on Yurubcheno-Tokhomskoye field with minimal mud losses and no well control events. This paper will present details about how MPD technology makes it possible to drill formations with narrow mud weight windows where traditional approach was ineffective. The application of MPD technology helped successfully drill wells while reducing non-productive time, improving performance, and increasing the safety for personnel.

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