Operators began evaluating the shale gas block in Central China since Dec 2010. During their exploration and appraisal phases, 3 horizontal wells were drilled. Their challenges consisted of hard, abrasive formations with kicks, losses, stuck pipe and over pressure. The problems were amplified by high geological formation dip, faults, and stratigraphic uncertainties. As a result, they were unable to achieve efficient drilling using conventional motor bottom hole assembly (BHA), that made it difficult to run casing, and multiple geological side-tracks were the norm. Naturally, these wells exceeded authorization for expenditure (AFE) curves, requiring an average duration of 200 days per well. This paper features the challenges and lessons learned along with the unconventional approaches that were employed to address these challenges. Four key categories of the process were identified:They consisted of emerging technologies such as a hybrid and robust rotary steerable system (RSS), real time rate of penetration (ROP) optimization and high resolution real time logging while drilling (LWD) image data tools. In addition, drilling and best practices adopted were managed pressure drilling (MPD), high dog-leg-severity (DLS) curve with smoother borehole, and low cost rotating blowout preventer (BOP) with higher revolution per minute (RPM). In the absence of 3-D seismic data, 2-D seismic data combined with LWD data were used. Integrated Operations & Innovative Commercial Contract with local drilling service contractors had made a big impact in terms of faster well delivery and overall cost saving. Another step change was with the performance based commercial contract that helped to attain the ultimate goal to meet health, safety and environment (HSE) and time requirements.At the end of 2013, 11 horizontal wells were drilled and completed. Amongst these, one well was categorized as Top Quartile and four were Best-In-Class. Additional highlights include significantly reduced geological side-track; quadruple footage drilled per day and the reduction in drilling cost. Average well duration was significantly cut to 110 days.These accomplishments consequently enhanced the drilling schedule sequence with longer horizontal wells being planned and greater confidence of predictability and repeatability.The paper will conclude with a summary of comparative learning statistics. The team believes that this is a big step towards delivering Best-In-Class wells in complex geological structure. The next step is to realize the ambition of factory drilling at a further reduced cost to tap the unconventional plays in the Sichuan basin, and bring cleaner fuel to Central China as a replacement of coal.
Horizontal drilling and sidetracking of existing wellbores is one of the main methods of production level increase on brownfields. This paper describes the engineering study on drilling performance enhancement conducted for a group of oilfields in Western Siberia, Russia, where the operator company has just started sidetrack and horizontal drilling campaign. The first several sidetracked wells drilled were characterized by high amounts of non-productive time (NPT) due to downhole tools failures and low penetration rates (ROP). For NPT root cause analysis, drilling surface logging data (including real-time torque and drag analysis) along with downhole measurement while drilling (MWD) vibrations data was analyzed and figured out the failures mechanisms. ROP improvement process included interpretation of LWD and wireline logs and their correlation with bottomhole assembly (BHA) performance via mechanical specific energy (MSE) approach. A number of factors that led to overall unsatisfactory performance on sidetracks were identified. This included wrong bit selection, limited drilling parameters, hole quality problems and cleaning issues and several others. These issues were properly addressed with field-proven drilling optimization process, which resulted in doubling of previously achieved ROP and elimination of NPT. The next sidetrack was drilled with 40% reduction of average rig days per 1000 m. Based on experienced gained, a motorized rotary steerable system (RSS) BHA was selected for the next complex sidetrack well, and provided another record-breaking performance, with another 20% improvement of ROP. The successful techniques are currently being transferred from sidetracks to horizontal sections on new wellbores. The paper represents latest achievements of ongoing drilling optimization process, which allowed the operator company to significantly decrease time and operational costs on drilling operations. The described complex geological and technological approach, along with revised wellbore placement, have led to main project performance indicators increase and next-step completion and production solutions for enhanced hydrocarbons recovery.
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