As fields mature, drilling can become more difficult. The likelihood of losses increases as reservoir pressures decline while higher mud weights are needed to prevent collapse of overburden shales as targets are pushed further from the platform. Drilling parameters for the Forties field have become fairly well established after years of experience yet 65% of the wells drilled between 2002 and 2007 experienced incidents attributed to instability. As field production declined, economic viability demanded a step change in performance. Through a better understanding of the field geomechanics and past drilling events, the Apache drilling team has implemented fit for purpose drilling procedures that have significantly improved drilling efficiency. This paper describes how geomechanics analysis has been used to assist well planning. Incorporating the experience of recent wells, the Forties mechanical earth model has been refined and provides key inputs needed to optimise well plans and adapt drilling practices to changing conditions. The adverse effects of anisotropy is a key reason for wellbore instability in the overburden. A joint Apache-Schlumberger team has been working to integrate geomechanics and geophysics knowledge of the field to quantify the effects of anisotropy related to bedding planes and weak shales. It can be difficult to predict drilling and completion risks during well planning, often due to the lack of distinction between events caused by formation instability and those which are drilling induced (drilling practices, hole cleaning). Capturing and classifying historic drilling events is a fundamental key process in understanding the mechanism and causes of well bore failures. Drilling performance in this mature field has been improved through the collaborative effort of Apache staff and key service providers. The refinement of the wellbore stability model has enabled sound practices and procedures to be developed.

Drilling horizontal wells in soft formations can pose significant risks that require careful planning and execution. During 2014, Virginia Indonesia Co. Limited (Vico) successfully completed two surface-to-inseam horizontal wells to appraise coalbed methane (CBM) production potential on their Sanga Sanga license in East Kalimantan, Indonesia. Both wells passed through soft shales and coals that exhibited breakouts in offset wells, in addition to heavily depleted zones exhibiting large fluid losses in an area well known for shallow gas blowouts. Geomechanical analysis of information from nearby offset wells was used to determine the mud-weight window and fluid properties required to effectively manage these conditions. The results were incorporated into the preliminary well design and planning, and with model matching carried out in real time while drilling operations were underway, any deviations in wellbore integrity were managed as they arose. The drilling success was, in large part, a result of extensive preplanning and a regimented approach to how the wells would be drilled and any instability dealt with promptly. In addition, real-time monitoring that identified deviations from model-based predictions provided invaluable information for planning subsequent wells. The methodical approach to planning and execution of these wells led to their successful completion, with the results potentially reshaping the Indonesian CBM and energy industry.

In a super-giant field onshore Abu Dhabi; the production strategy is to maintain the sustainable capacity but due to increase in water production the need of artificial lift is mandatory to maintain the production plateau. However, accurate well integrity management in such field is critical due to fluid characterization, souring environment and field extension (35 X 20 Km).The selection of the artificial lift technique plays an important role in improving the ultimate recovery. However managing the integrity of the artificial lift wells is more challenging under the presence of H2S, CO2 and high P & T. The loss of production caused by integrity related issues and the need to determine specifications and accurate future integrity management plan lead to need for a gas lift pilot. For the future it is envisaged that integrity assurance plans needs to be an integral part of the field-development planning, ensuring that asset value is maximized.More challenges will exist when dealing with Gas Lift as it is a long term artificial lift technique affecting well design for long life completion. Therefore, Gas lift was piloted to better understand real integrity challenges and measure corrosion trends with time to gain operational and technical experience and to compare them with initial theories.The pilot was monitored closely with intensive program. An optimization process was followed, assisted by modelling. Although the initial thought that the corrosion might affect the top part of the completions because of the injected gas specification, but the time-laps corrosion logs gave a completely different and unexpected picture. The pilot results enabled the overall project to be concluded; the lessons learnt from the pilot were captured and used as building block for the full-field development options.The paper describes the pilot results, the integrity challenges and the contoured problems, the philosophy of monitoring the corrosion evolution, the findings and how it was different from the initial expectation. Finally the clear impact on the integrity management process to ensure proper long-life well design and completion strategy.

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