Directional casing while drilling (DCWD) utilizing a rotary steerable system or a steerable positive displacement motor is a recent enabling technological application of proven casing while drilling. DCWD has been successfully applied in wells in the North Sea and Middle East using both rotary steerable systems and PDMs, proving up its operational reliability. The technology has most recently been utilized in a project from a producing platform in the Asia Pacific region. While this DCWD application increases the challenges of directional drilling, the project was completed successfully in terms of increasing ROP and lowering the time and cost to drill the top hole section of the well. Top hole directional drilling of wells in high density locations such as multi-well producing platforms require carefully planned, detailed procedures and reliable techniques to result in a safe and efficiently drilled wellbore. The procedure, in addition to directional capabilities, requires that the well meet the demands of anti-collision concerns within the torque and hydraulic operating parameters of the formation. The drive for continuous improvements led the field operator to choose DCWD technology to deliver step changes in drilling performance while meeting the company's strict operational and safety directives. The successful effort was a carefully planned and implemented operation that required the close cooperation of the operator, directional drilling company and drilling contractor during the entire procedure. This close interaction between all parties led to three world records and the world's first application of another enabling technology, including:World's deepest 13 3/8?? DCWD job;World's highest angle directional well with 13 3/8?? DCWD;World's fastest rate of penetration for a 13 3/8?? DCWD;World's first application of Gyro MWD with DCWD.
The Verkhnechonskoye (VCNG) oilfield located in Eastern Siberia is developed on pad clusters, with in excess of 200 wells drilled to date. Typical well geometry consists of a vertical 13 3/8in. conductor followed by directional 12 ¼ in. and 8 ½ in. sections ran with subsequent 9 5/8in. and 7in. casing strings. Production hole is drilled in 6in. with a 4 ½in. liner set prior to completion. The predominant well design incorporates a double build profile which lands horizontally in the Verknechonskiy reservoir with an approximate 600m lateral drilled in the productive zone. VCNG field has evolved of key strategic importance to deliver oil through the Eastern Siberia Pacific Ocean (ESPO) pipeline from Russia to the vast Asia-Pacific market located to its South East. Increasing production targets have been required to deliver hydrocarbons to fulfill aggressive pipeline commitments. Meeting these requirements have in turn initiated a relentless drive to enhance operational efficiency since the inception of development drilling phase in 2007; leading to a significant increase in drilling performance and reduction in overall well construction time in the period to date. This improvement has been achieved against the backdrop of an environment which is extremely challenging on several distinct fronts; remoteness of the project with >600km from the nearest major conurbation, harshness of an extreme continental climate with temperatures seasonally dropping to -50°C and coupled with a unique and problematic lithological column all serve to make drilling, logistics and general operations a complex undertaking. The purpose of this paper will be to take a holistic review of drilling performance in the field and to chronicle the numerous incremental technological and procedural advancements which have led to a reduction in average well construction time from 58 to 21 days between 2007 and 2011. Incorporated into this dramatic efficiency improvement includes a 465% increase in average well ROP along with a corresponding increase in meters drilled per circulating hour (MPCH) of 390%.
The Vankor oil and gas field in Eastern Siberia is predominantly developed using horizontal wells drilled into the upper Yakovlev and lower Nizhnekhet formations. The field development scheme consists of pad clusters resulting in complex well trajectories. Due to the remoteness of the field and resulting complex logistics, any directional drilling technology deployed to deliver the complex trajectories must be robust and reliable. Traditionally, the wells have been drilled with steerable positive displacement motors; in 2008, rotary steerable tools where introduced along with logging-while-drilling (LWD) technology and this provided significant performance improvements in the 8.625 in. and 6 in. sections. To further improve on drilling performance, an engineering study was conducted in 2009 to assess other opportunities for increasing the annual cumulative meters drilled on the project. Several areas of opportunity were identified and prioritized in terms of ease of implementation and expected impact on drilling performance; a key recommendation of the study is the introduction of powered rotary steerable system (PRSS) bottomhole assembly (BHA) in the 8.625 in. section. The PRSS BHA recommended for this application is a tandem rotary steerable-positive displacement motor BHA where a straight fixed housing positive displacement motor is placed directly behind a push-the-bit rotary steerable tool.Various configurations of the PRSS BHA design have been used in other applications including vertical control 1 , performance drilling 1,2 , coiled tubing drilling 3 and directional casing while drilling 4 . In most cases it demonstrated the capacity to deliver better drilling performance in terms of penetration rates and directional control that outperforms conventional directional drilling systems. In the case study wells presented in this paper, about 200% improvement in rate of penetration (ROP) was achieved with an average of eleven operating rig days saved per 8.625 in. well section. The total drilling cost savings realized is estimated to be about USD 1,300,000.00; this is based on an average rig spread rate of USD 40,000.00 per day. These are good results and represent a step change in drilling performance in the field. Some limitations of the new system were also observed in the case study wells, they include inability to deliver consistent dogleg severity (DLS) in excess of 3.5°/30 m, rig hydraulics capacity constraints that limit its broad application, restrictions on bit selection and constraints on the available drillstring rotary speed caused by the unique BHA configuration that in some cases complicates hole cleaning planning. This paper discusses these results and key performance indicators, including aspects of the BHA design, bit selection, hole cleaning management, wellbore stability and drilling practices. A new technology solution to the dogleg severity limitations is proposed: a new generation hybrid rotary steerable tool that can deliver DLS up to 15 o /30 m. It can be incorporated in new tandem rota...
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