Abstract

The Yurkharovskoye oil and gas condensate field is one of the main asset of PJSC NOVATEK. Two of the three productive levels (Cenoman and Valangin) are in the active development phase. The Jurassic reservoir, which is characterized by complex geology, high formation pressure (gradient ~ 2.0MPa / 100m) and a low fracturing gradient (FG), is currently in the exploration phase. In 2017, drilling of the first exploration well with a depth of 4855 m with a horizontal ending with multistage formation fracturing in the Jurassic formation was successfully completed. Successful completion of the drilling allowed not only to obtain valuable geological information, but also to choose an approach to the construction of such wells in the future.

Joint efforts of the field operator, drilling contractor and oilfield services company have developed a drilling system that included a full range of engineering solutions that ensure an efficient and accident-free well construction process: completion, directional drilling, bits, drilling fluids, geomechanics and managed pressure drilling (MPD). Previous experience in the construction of directional wells was associated with mud losses due to fracturing, blow outs and wellbore collapse. At the design planning stage, the well design was optimized, the completion system was developed, the formulations of high-density drilling muds with low rheology were selected, a choice of technologies was made and much more. Each stage of the well construction was worked out and a scheme of operative interaction between the parties was developed, which allowed timely correction of the work program based on an actual information.

Even at the design planning stage geomechanical modeling allowed design optimization and choose a safe trajectory of the well, and its update, based on the actual information, allowed to reduce the risks. Specially for this well, the formulation of the hydrocarbon-based solution was developed, which, despite its high density, was distinguished by low rheological properties. An important aspect of the preparation was the selection of bottomhole assembly and drilling regimes, which, on the one hand, should ensure efficient drilling, and on the other, generate the smallest possible equivalent circulation density (ECD). The use of MPD technology has made possible to maintain the ECD and ESP (equivalent static pressure) at the same level and to compensate for the pressure fluctuations during circulation and movement of the drill string while trips. To select the BHA, a special program complex was used to simulate the dynamics of its behavior at the bottomhole. Logging tools at BHA provided important real-time information that was used to manage the drilling process and make operational decisions. The hybrid rotary steerable system (RSS) allowed to drill the well in the riskiest intervals with a minimum angle and to provide a high dog leg and hit the target. The completion system for multistage fracturing with swellable packers required preparation of the wellbore and planning of all the necessary operations in order not to initiate hydraulic fracturing, wellbore collapse and failure to reach the target depth.

The project of NOVATEK-Yurkharovneftegaz is a bright example when modern technologies and effective interaction of participants allow successfully solving problems that were previously considered as difficult to implement and open new horizons for developing hard-to-reach deposits in extreme conditions. Successful experience gained during the project will ensure the efficient construction of wells in the field.

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