Annular fluid or gas migration, resulting in surface hydrocarbon leaks or sustained casing pressure (SCP), is a problem operators face worldwide. With energy demands escalating, it becomes increasingly important to maintain production from existing wells and bring new wells on line without delay. Internal company policies regarding health, safety and environment, along with increased government scrutiny of the petroleum industry, can require wells to be shut-in if leaks or SCP are present. Estimates of the number of leaking wells have varied widely as reporting standards have evolved over time and from country-to-country. In Western Canada, however, there are detailed reports of over 18,000 wells having Surface Casing Vent Flow (SCVF) that in some cases requires them to be shut in and production suspended. From spud-in to abandonment, an oil well is subjected to numerous, repeated events that could compromise zonal isolation. Resulting damage, in the form of cracks in the isolation material or the creation of a microannulus, can allow hydrocarbons to flow to surface or become trapped below the wellhead. This paper will describe a novel zonal isolation material that responds to a loss of hydraulic isolation. If hydrocarbon flows occur within or around the primary cement sheath, the material will seal these flows and re-establish well integrity. The system, which has slurry properties comparable to standard oilfield cements, is designed to be pumped as part of any primary cementing operation on wells drilled with water or oil-based drilling fluids. This material was used in well construction operations for wells drilled in Eastern Alberta, and can be applied to reduce the incidents of SCVF in this area. This ability of this system to eliminate hydrocarbon flows has been confirmed with high-pressure laboratory testing, and it has been successfully field tested in Western Alberta. Introduction As worldwide demand for petroleum continues to increase, operators face the challenges not only of finding new reserves of oil and gas, but also of maximizing the productivity and longevity of the wells that are drilled into existing reservoirs. According to the International Energy Agency (Oil Market Report 2007; Press Release 2006), worldwide petroleum demand is expected to increase by 13.9 million BOPD, from the current level of 85.9 million BOPD to 99.5 million BOPD, over the next seven years. By contrast, production has increased by only 6.7 million BOPD over the last seven years (Short-Term Energy Outlook 2007). If the industry is to keep pace with this demand, operators will have to look at ways to maximize returns from individual wells, in addition to improving overall reservoir recovery. Great advances have been made in cementing practices over the years. These advances include improvements in fluid displacement modeling as well as the development of slurries with improved chemical and rheological properties. These advances have gone a long way towards improving hydraulic isolation, but they do not address damage to the cement sheath that may occur days, months or years after the cement has set. This potential for loss of hydraulic isolation during or after a well's productive life represents a weak link in hydraulic isolation. A damaged cement sheath can allow the migration of hydrocarbons, which can reach the wellhead in the form of sustained casing pressure (SCP) or surface casing vent flows (SCVF), potentially requiring a well to be shut-in, repaired or abandoned prior to the end of its productive life.

Well barriers are an important factor during the life of a well. As cementing is involved in many of those well barriers, there is considerable focus in the oil field on the design, execution, and validation of the cement as a well barrier. It is important that the cement job design begins at the same time as the basic well design, especially in deepwater operations. Decisions made early in the well design can have a tremendous effect on the cement job execution. Early in the well design, the cement job objectives are set, and through simulations, the cement job placement, slurry design, and, in some cases, well design, are optimized to overcome any identified challenges and minimize risks during cement placement. Cement equipment is becoming increasingly more sophisticated and cement job designs more critical; additional attention needs to be placed on the cementing job preparation on location prior to the actual cement job. By using the latest advances in communications, it is easier for the offshore cementing specialists to stay in contact with the shore-based staff; not only with the design engineer, but also the maintenance manager or operation support staff. Improved monitoring and automation during the job execution enhances the process control. Advances in real-time capabilities enable the onshore experts to monitor the offshore operations and provide advice during the execution of the cement job itself. The final step of a cement job is the evaluation phase. A cement job evaluation is more than just a pressure leak-off test or running a cement evaluation log. The evaluation procedure of a cement job ties together all the parameters of the job, including the job objectives, drilling parameters, job execution, and post-job test results. Looking at one parameter only will often not provide a complete analysis and evaluation. Because cementing provides critically needed well barriers, it becomes a very important aspect in well integrity management during the life of the well.

In a traditionally cemented well, the integrity of the cement sheath surrounding the casing, and the bond between the cement and the formation or casing are essential components of hydraulic isolation. A well-cemented casing is designed to maintain hydraulic isolation throughout the productive life of the well and after abandonment. With advances in cementing technology, slurries have been designed that result in cement sheaths that can resist planned wellbore stresses without failure. Once the cement has set, however, the fixed set-cement properties do not address stresses that have not been planned for, and that may ultimately result in cement sheath failure. This study considers the case of well construction as part of a new gas field exploration in Algeria. Wells drilled in this area have been prone to developing annular gas leaks in the weeks and months following cementing operations. To prevent the loss of isolation and reestablish hydraulic integrity in the event of cement failure, a new cement-based sealant was incorporated into the well construction plan. This reactive material responds to hydrocarbon leaks that occur because of fissures in the cement, debonding of cement from the formation or the development of a microannulus between the cement and the casing. These leaks trigger a self-healing response, sealing the leak path, and restoring well integrity. Using this sealant material has reduced the incidence and likelihood of leaking wells in an area where such problems are common, and eliminated the potential time and cost associated with leak remediation. Introduction As is the case in many oil producing countries, oil and gas development in Algeria has accelerated greatly in the last few years. With proven gas reserves of 4.55 × 109 m3 (160 Tcf), representing approximately 3% of the world's total, and easy access to European markets, Algeria has endeavored to increase gas production to meet the demands. Statistical data from Sonatrach, the national oil company of Algeria, shows that from the period 1996–2006, yearly natural gas production increased by 19% to 1.5 × 108 m3 (5.3 Tcf), with yearly oil production increasing by 69% over the same period to 6.37 × 107 Mg (approximately 460 million bbl). As such, Algeria is becoming an important energy provider for Europe, supplying 6.1 × 1010 m3 (2.1 Tcf) of gas in 2006. According to the BP Statistical Review of World Energy (2008), this represents just over 12% of the European Union's total consumption, and could be considered a valuable source as Europe seeks to diversify its gas supply. The drive to increase production and exports has led to a predictable increase in drilling activity. The gas fields located in the In Salah area of the Tamanrasset Province, shown in Fig. 1, are considered important to the continued increase in the country's export capacity. Conditions in this area can be very harsh—an isolated desert environment where summer temperatures average above 45°C (113°F), and winter temperatures dip to near freezing—but Sonatrach has undertaken an aggressive exploration and development campaign in the area. The remoteness of the field, as well as the need to maintain production, makes it complex and costly to perform workover operations to repair wells in the event that there is a loss in hydraulic isolation. Annular leaks and sustained casing pressure (SCP) can result in just such a workover, and it is the ultimate goal of most, if not all, primary cementing operations to prevent such fluid migration from occurring behind a cemented casing. Current cementing technologies, which for the most part focus on placement techniques and the properties of the liquid slurry, are limited in their ability to prevent liquid or gas migration that may occur due to cement damage or debonding that may occur long after the cement has been placed and has set. This paper will describe the use of a new cementing material with intrinsic, self-healing properties first proposed by Cavanagh et al. (2007) as a means of assuring well integrity in the event of hydrocarbon leaks due to damaged or de-bonded cement. This self-healing cement (SHC) has the ability to respond to hydrocarbon leaks, either liquid or gaseous, occurring after the cement has set. Examples will be presented where SHC was used to prevent annular gas leaks in wells that had previously been difficult to isolate using current cements and placement techniques.

Ever increasing energy needs have encouraged the operators to explore newer areas in deepwater. One of the high potential areas under exploration is the Caribbean basin, which includes Trinidad and Tobago, Suriname, Guyana and French Guiana. Due to the extreme environmental impact that can result from incidents occurring offshore, well integrity is a critical element in offshore development.. Cementing plays a major role in ensuring well integrity and this paper will cover various cementing challenges that were faced in Caribbean deepwater zones. The water depth of wells in Caribbean can be as much as 2300m with seabed temperature of about 4 ºC causing complex heat transfer and requiring fluid modeling software to accurately predict the bottom hole circulating temperature (BHCT) profile. Deepwater wells in the Caribbean can also be affected by the formation of gas hydrates. Cementing in hydrates requires cement slurries with low heat of hydration (HOH). The results from several field studies were used to select an optimum slurry design to successfully cement in hydrates. The wells in this area are also characterized by low fracture gradients with a narrow window between fracture and pore pressures. The cement jobs are designed with advanced computer aided design (CAD) to accurately simulate equivalent circulating density and assist in designing fluid placement within this narrow window. Engineered lost circulation material (LCM) can be used in fluids to achieve successful cement placement. Fluid modeling software also helps in optimizing mud removal by simulating the impact of centralizer distribution, optimizing spacer properties and more. To evaluate cement placement a combination of advanced acoustic logging-while-drilling (LWD) tools and pressure analysis can be used for deeper sections while for riserless sections, visual feedback from remote operating vehicle (ROV) can be used. A case study from Trinidad and Tobago and Southern Caribbean highlights some specific solutions and lessons learned.

The development of arctic resources requires wells to be drilled, cased, andcemented through permafrost. Permafrost presents unique challenges, especiallyto cementing operations, requiring a cement system with the capability toperform in the subfreezing permafrost environment. The performance required isthat the cement provides isolation, exhibits low heat of hydration, and setswith sufficient strength to provide casing support. There are also specifictesting requirements detailed in API recommended practices. In the polar region, there are several approaches used in the design of cementsystems. The approaches used in Russia, Canada, and USA (Alaska) areillustrated. The design considerations take into account local conditions andrequirements and use knowledge from cementing practices employed in thedrilling industry. It is important to understand the current cementing practices in use withinthe arctic region. This will allow future improvements as more developmenttakes place and the resources become exploited. Introduction To be successful, hydrocarbon resource development in arctic regions mustmeet the challenges posed by drilling, casing, and cementing wells throughpermafrost layers in the remote arctic environment. The Russian Far East, forexample, is almost completely covered in permafrost and holds significant gasreserves that remain largely untapped due to the remoteness of the area and thecomplexity of drilling through the permafrost layers. Offshore operations areadditionally impacted by sea ice, which does not directly affect cementingoperations; however, the short operational window certainly requires detailedplanning and reliable performance. The remoteness of arctic locations affects all aspects of development, impacting overall logistics: access, timing, and materials delivery andstorage. In addition, several of the challenges faced during the initialdevelopment phases affect the subsequent cement job and cementing practices. These challenges need to be addressed as part of the overall development plan;they include borehole maintenance, casing centralization, and mud conditioningand removal, and all require careful consideration of the permafrost.