Cementing gas wells in Khuff reservoir where sustained annular pressure has been reported in many wells, presents a big challenge offshore in Umm Sheif field in Abu Dhabi. The main challenges are preventing gas migration and achieving long-term zonal isolation using a competent cement sealant system able to withstand downhole stresses and high temperatures during production cycles. An extensive study was carried out on two previously cemented wells, and an in-depth analysis was performed on the cement systems pumped in this field. The knowledge gained paved the way for designing, planning, and executing successful cementation on a recent well. A mathematical model simulating downhole stresses in terms of pressure and temperature was used in designing the cement sealant system. Unlike conventional cement systems, properties such as high Poisson's ratio and low Young's modulus value compared to that of the rock were optimized in the new system to achieve mechanical resistance and durability. This paper describes a case history whereby this cement sealant system was used to cement and secure the critical phases of this well. Cement evaluation logs across all the liners showed complete cement coverage and zonal isolation, especially across the Khuff gas reservoir. Introduction Any well containing a gas bearing formation is a potential candidate for annular gas migration. Cementing wells with potential gas migration is a critical operation. It requires from both service company and operator full and complete cooperation to gather the necessary data in order to optimize the design of the cement slurry, as well as its placement to mitigate the risk with the gas migration. The severity of gas channeling or migration can range from the most hazardous, blowouts, to less severe cases of residual gas pressure of a few psi at the wellhead. The main concern is the gas migration behind shallow casing strings or behind long liners For shallower casing strings cemented to surface the slurry volumes are usually large, holes are washed out, centralization is poor and frequently the fracture gradient will not allow the pumping of heavier fluids. For liners, more attention is usually paid to design and mud removal, however long liners pose problems of large temperature differentials between the top and bottom sections. This poses problems when the gas zone is near the top of the liner section.

Offshore cementing poses many challenges across the world as drilling oper ations move towards deep-water and ultra -deep-water. As a new initiative of continuous improvement, a deep-water cementing peer review process was started early 2011. To this date, th is team has reviewed more than 12 00 deep-water cementing jobs in more than 30 countries worldwide.

Deepwater cementing poses many challenges across the world as drilling operations move towards greater water depths. The Deepwater Cementing Review Team (SPE WVS 035), gathered to provide oversight to the deepwater cementing job programs within the corporation and to insure they meet the industry standards, has reviewed so far more than 1200 jobs spread over 30 countries worldwide. About 10% of the reviewed jobs are riser-less surface casing cement jobs. When present, shallow flow is one of the biggest risks in cementing surface casings. Not achieving zonal isolation can result in the loss of the well or expensive remedial work. Early identification of potential shallow flow is crucial as it gives time to optimize the cement job following industry best practices, such as API RP 65 and API ST 65 – Part 2. Three important factors for a successful cement job in case of shallow flow are proper centralization, good mud removal and slurry selection. If shallow flow is present, the surface casing must be properly centralized to achieve flow around the entire casing. Conventional cement systems are widely and successfully used for surface casings. However, if shallow flow is identified, more advanced cement systems, such as foam cement or optimized particle-size distribution cement, are used. Zonal isolation of shallow flow zones can be obtained through cementation when the engineering guidelines are followed and focus is placed on proper design and execution. A statistical analysis of the surface casing designs reviewed shows the risk of shallow gas and demonstrates that shallow flow can be prevented, after the flow potential is identified. The key is early identification of shallow flow and open discussion between the operator and the service company.

One of the main challenges of drilling in the Central Andaman Sea offshore Myanmar is the mitigation of overall well integrity risk arising from weak top-hole formations. On a well drilled by one operator, conductor integrity was lost due to cratering and loss circulation while cementing which eventually led to having to re-spud the well. Almost all the offset wells drilled by the operator in the same field experienced losses in the top section interval.To meet integrity objectives for both exploration and development wells, the cementing strategy in certain cases must consider alternative solutions in addition to conventional Class G cement. In a recent project executed for one operator the cementing philosophy for the entire surface sections therefore had to be fine-tuned to incorporate the proven Optimized particle-sized distribution methodology.A proprietary coarse material made from glass beads was introduced as part of the slurry design, being used for the first time in Myanmar to further improve cement properties. On the development wells the optimized design called for pumping 10.5ppg High-performance Light-weight cement (HPLWC) lead slurry, together with a standard Class G tail.To meet operational integrity objectives, planning and risk assessments were put in place by the service company and the cementing programmes were developed to incorporate necessary mitigations against the identified risks. Plans were put in place to handle the implicit logistics requirements. Careful attention was paid to the execution given the downhole pressure sensitivities, all slurries were mixed and pumped with a degree of relative precision. This paper summarizes the design and implementation of the cementing operation which contributed positively to meeting well integrity objectives. Apart from operational success, expectations which hitherto factored in possibility of top-up jobs were exceeded; for the exploration well the critical zones were covered with good returns to seabed observed on all the cement jobs as monitored by ROV. Hard cement were tagged and drilled out from the shoe track in each case and well operations progressed without any loss of integrity issue.The paper aims to demonstrate that incorporating technology can help to improve well delivery and reduced lost time. Approximately, 18 cement jobs have been executed on the project -all successfully done. Out of these 4 top-hole cement jobs involved the use of the High-performance Light-weight (HPLWC) technology described in this paper.

The deepwater drilling industry continues to require increased oversight of cementing programs and cement operations. A deepwater cementing technical specialist team was created to provide reviews and oversight of deepwater cement programs worldwide. Deepwater cementing specialists were selected from within the organization and the initiative was introduced to operations in the first quarter of 2011. The team provides an additional level of peer review of all deepwater cementing programs. The purpose of the peer review is to support the engineer's program design and to verify that the program is in compliance with internal standards, client standards, and applicable regulatory requirements. If required, the team will act as a liaison for the operations personnel and additional experts on critical jobs. The reviews are documented so that all communication can easily be tracked.The main objective of the team is to provide a proactive approach to identify risks early in the design phase and elevate the risks to the appropriate levels of management so that appropriate actions can be taken. The goal is to review all deepwater cement programs before submitting the final procedures for operations.Sharing worldwide knowledge and adding to the worldwide knowledge base is necessary as new challenges are faced while drilling and cementing offshore wells in deep and ultradeep waters. Risks and potential hazards may be recognized long before the job execution-giving sufficient time to change, improve, and enhance the cementing design. Several examples are given for job designs that have been improved prior to execution. As a result of this initiative, a continuous improvement of job procedures is being observed worldwide, resulting in designs with a higher likelihood of achieving the job objectives, and avoiding unnecessary, costly remedial work.