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A number of cementitious materials used for cementing wells do not fall into any specific API or ASTM classification.These materials include: Pozzolanic materials include any natural or industrial siliceous or silico-aluminous material, which will combine with lime in the presence of water at ordinary temperatures to produce strength-developing insoluble compounds similar to those formed from hydration of Portland cement. Typically, pozzolanic material is categorized as natural or artificial, and can be either processed or unprocessed. The most common sources of natural pozzolanic materials are volcanic materials and diatomaceous earth (DE). Artificial pozzolanic materials are produced by partially calcining natural materials such as clays, shales, and certain siliceous rocks, or are more usually obtained as an industrial byproduct. Pozzolanic oilwell cements are typically used to produce lightweight slurries.
In 2019, a well operator in North Sea UK executed a conductor batch drilling and cementing campaign consisting of eight 28-in conductor casings. With the aim to further optimize the cementing operation efficiency and reduce wait-on-cement (WOC) time, thus helping the operator to reduce drilling time to complete this batch drilling campaign, the cementing service company used an integrated approach with the application of dual-component cement blend with high compressive strength development and inner string stabbed-in cementing technique in this conductor batch cementing campaign.
The common cementing objective for conductor casing is to provide structural support for the wellhead by having the top of cement in the annulus at the seabed, depending on the well fatigue limit analysis result. With the weak unconsolidated formation at shallow depth and the low seabed temperature, the challenge was to provide an engineered cementing solution with high early compressive strength development rate at low temperature and of lighter density to avoid fracturing the weak formation. The cementing service company formulated a dual component cement blend to provide such a cement slurry by combining the rapid hardening cement and hollow silicate spheres. To further optimize the drilling operation efficiency from cementing perspective, an inner string stabbed-in cementing technique with double float casing shoe was used to eliminate the time to drill out cement left inside the casing shoe track.
The 36-in. open hole section was drilled to 310 m, and 28-in. conductor casing was cemented with a lightweight rapid hardening cement slurry. The cement slurry density was formulated at 1.5-SG with seawater as the base fluid to further accelerate the setting time and compressive strength development of the cement. This paper discusses the risk assessment and safety factors that were considered in the cement job design phase, including the laboratory testing that was carried out according to
The conductor casing batch cementing job successfully met the well timing objective set by the well operator. An estimated 96 hours was saved from the conductor batching campaign with this integrated approach to optimize operational efficiency from cementing perspective. This paper will help to establish a solid case history for well operators to further improve the drilling operational efficiency for conductor drilling.
Susliakov, Ivan (Technology center Bazen, LLC) | Shevchuk, Taras (Technology center Bazen, LLC) | Alekseev, Alexey (Technology center Bazen, LLC) | Dryaba, Alexey (GROUP MTO, LLC) | Alyakin, Andrey (GROUP MTO, LLC) | Sekachev, Oleg (PNG Service Company Ltd)
Abstract Significant progress in technologies development of well completion and stimulation allowed to involve in the development of reserves which 10 years ago were considered unpromising due to the too low reservoir permeability. Particularly significant influence of modern achievements on shale beds, which were previously not seriously considered as possible objects for hydrocarbon production. The success of shale oil production in the United States inspires oil companies around the world to study the possibility for the development of such objects. On the territory of the Russian Federation is perhaps the largest area of shale formation of the world – Bazhenov formation. In 2016, PJSC Gazprom Neft for the first time for the Bazhenov formation implemented a full cycle of construction of a horizontal well with a Multi-Stage Fracturing, which on the level of the applied technological solutions is not inferior to the American analogues used in the United States for shale oil production. The length of the horizontal section of the well was more than 1000 m; the 114 mm liner OD was run in and cemented. The cementing operation was carried out with liner rotation, and the cement blend itself contained specially selected additives which were designed to ensure high resistance of the cement stone to the damaging effects from multi-stage fracturing. The experience in drilling and cementing, completion and production operation of the well turned out to be positive, and in 2018, a pilot project started drilling a whole series of horizontal wells with multi-stage fracturing at two well sites. During the implementation of the project was found a stable relationship between the well production and the efficiency of fracturing, which is significantly affected by the isolation the anulus.
Rollins, Brandon (Whiting Petroleum Corporation) | Lauer, Travis (Whiting Petroleum Corporation) | Jordan, Andrew (BJ Services) | Albrighton, Lucas (BJ Services) | Spirek, Matthew (BJ Services) | Pernites, Roderick (BJ Services)
Abstract Frequently exposed weak formations require the use of lighter slurries, and with increased wellbore pressures encountered during fracture stimulations, stronger cements are essential. Lighter, stronger cementing technologies are the key to ensuring well integrity and enabling simple, cost-effective well construction designs. This paper describes the benefits and features of newly developed, lightweight cementing materials available for operations in the Williston Basin. Applications of these materials are supported by case histories and extensive laboratory test data. Regionally, materials have been identified that can be used to produce innovative, bulk lightweight cementing systems. These materials can be inter-ground with the cement during manufacturing or blended with bulk cement. Both methods create cost-effective, high-strength cement systems that can easily be formulated into slurries with densities as low as 10.5 ppg. Comprehensive laboratory test data was generated to support well simulations and field trials of the new materials. Field trial data is then analyzed to illustrate the benefits of cement systems. Economical lightweight cements are commonly produced with fly ash extended systems, however, these systems have low strength at low densities. Lightweight, high-strength, fit-for-purpose cement materials are common in southern oil and gas basins, but transporting these materials to northern states is cost prohibitive. Exotic solutions to create lightweight cements (nitrogen foams or hollow glass micro-beads) are available but expensive, adding considerable operational complexity. Laboratory data demonstrates mechanical properties of the cement systems, slurry properties and set characteristics. The new, low-density cement systems show far greater compressive strengths than conventional blends. Conventional slurry provides a compressive strength of 500 psi, whereas the new low-density 12 ppg blends provide compressive strengths greater than 1,000 psi. Additional practical benefits of these systems are illustrated by varying water content to improve slurry density from 11 to 13.5 ppg without additional cementing additives. Multiple case histories illustrate the results of the applications of these materials at downhole temperatures ranging from 140°F to 220°F and well depths up to 11,000 ft TVD in the Dakota, Mowry and Charles Salt formations. The limitations associated with traditional cementing materials will no longer restrict the creation of efficient well designs in northern states with the implementation of new, low-density cement systems necessary to exploit these oil and gas basins. Using lighter, stronger cement technologies will provide simple, cost-effective designs that are needed to ensure wellbore integrity in the Williston Basin.
Abstract Lightweight cements offer significant performance benefits over conventional higher density cement blends, including; improved mechanical properties and stress resilience, lower thermal conductivity, lower ECDs and improved returns to surface and potentially lower risk of casing collapse due to trapped annular pressure. However, a number of challenges exist in developing lightweight blends for thermal applications specifically concerning achieving short wait on cement at low bottom hole static temperature while also ensuring long-term chemical and mechanical stability at high temperatures. Here we report the development of a new lightweight thermal cement by utilizing hollow glass microspheres. Further fine-tuning of the desired slurry properties including controllable thickening times, zero free water, low fluid loss and short WOC was achieved through cost-effective additive adjustment, and the mechanical properties of the cement we validated by long term curing at both ambient and high temperaures (340 °C). To ensure that the high performance achieved in the controlled lab environment was maintained once deployed at full-scale field level an extensive QA/QC program was undertaken. This process involved collecting dry bulk field samples and confirming performance (thickening time, free water, rheology and fluid loss) prior to every job. After initial optimization of the blending process, a 100% success rate was achieved over the course of a more than a twenty jobs. Overall, a high quality lightweight thermal cement with excellent long-term mechanical properties was successfully developed and deployed.
Engelke, B.. (Schlumberger) | de Miranda, C. R. (Petrobras) | Daou, F.. (Schlumberger) | Petersen, D.. (Schlumberger) | Aponte, S. A. (Schlumberger) | Oliveira, F.. (Schlumberger) | Ocando, L. M. (Schlumberger) | Conceição, A. C. (Petrobras) | Guillot, D.. (Schlumberger)
Abstract In a joint effort, an oil and gas operator and a service company have undertaken research to help overcome well integrity and cementing fluids challenges in the presalt wells of Brazil where some fields present high levels of CO2 in reservoir fluids. Results are provided from the laboratory phase to cement placement evaluation. The new approach is to provide a cementing system that is not only resistant to CO2 attack but also has a self-healing capability in the presence of fluids containing CO2. The validation of the CO2 selfhealing and resistant cement technology was initiated at laboratory level. Then, a yard test with real-time field parameters was performed, proving that the new slurry can be mixed and pumped using conventional cementing equipment. Finally, an onshore well in Brazil served as a test well for deploying and evaluating the new CO2 self-healing and resistant cement system in the field. The technology consists of an engineered particle size distribution (EPSD) blend containing a reactive material that swells upon contact with CO2. This swelling allows the closure of microfissures and/or the reduction of the microannulus, which heals the cement sheath and reestablishes the integrity of the well. Then, a large-scale yard test was performed to evaluate real-time field parameters such as the fluidity and homogeneity of the dry blend and the mixability of the slurry using conventional cementing equipment. After the success of the yard test, the technology was deployed in Brazil. During the field test, 8 m [50 bbl] of 1,900 kg/m [15.8 lbm/gal] CO2 self-healing cement was pumped downhole and placed in the annular space between a 7-in. casing and a 8.5-in. open hole to promote casing support and zonal isolation in the production zone. The CO2 self-healing and resistant cement overcomes the deficiencies of conventional Portland cement in carbon dioxide environments and presents an advantage over other available technologies designed to withstand CO2 attack by maintaining zonal isolation and long-term well integrity. Moreover, this technology can be applied in any field in the world where CO2 is regulated and/or entails risk for operators or the general public.
Abstract Shell has experienced production casing deformation on several infill wells in an existing thermal development project in Canada. A full investigation identified trapped annular pressure (TAP) caused by unreacted water fraction in set cement between casing strings as a potential casing failure mode. A novel and innovative application of an existing technology (a cement blend incorporating hollow-glass microspheres) was developed, tested and implemented as an effective means to provide pressure relief in the cemented casing-casing annulus on steam injection wells. Thermal cement blends from two suppliers were used in the testing program. The test slurries were cured in a test cylinder until compressive strength development tapered off, and then heated in increments to 320°C while pressure was recorded. Typical thermal blends containing a range of concentrations of hollow-glass microspheres were tested in this manner to establish a slurry design that would prevent the pressure build up from surpassing the temperature de-rated collapse resistance of the casing. The tests using typical thermal cement blends with no glass bead additive resulted in rapid increase in pressure as the test cell was heated, and exceeded the temperature de-rated collapse value of the production casing string at temperatures much lower than typical steam injection temperatures. Tests performed on blends containing the glass spheres showed consistency and repeatability in results, and pressures were well below the de-rated collapse pressure of the production casing string at the maximum steam injection temperature. Based on preliminary results, this investigation has concluded that the cement blend containing 10% BWOC hollow-glass microspheres is a viable alternative to conventional thermal blends, capable of providing hydraulic isolation to meet regulatory requirements and industry best practices, with the added benefit of providing a mechanism to mitigate TAP on steam injection wells.
Abstract The integrity of thermal in situ wells is a function of the distinct yet inter-related processes that control the integrity of the reservoir caprock and of the wells themselves. Our objective was to bridge the scale gap between reservoir caprock integrity analysis and thermal well cement sheath design, and in so doing, improve the risk analysis of cement sheath integrity. At the well pad scale, a coupled finite element geomechanical model was used to predict the evolution of thermal and mechanical stresses in the caprock due to thermal in situ operations. The geomechanical models were populated with data from public domain reports from northeastern Alberta thermal in situ projects. These model results were then used to constrain a risk-based analysis of the multiple potential failure mechanisms at the wellbore scale that can compromise cement sheath integrity of thermal wells. Common thermal well and cement blend properties were used to then analyze the probability and magnitude of cement sheath damage during thermal injection operations. Although integrity may be predicted within the caprock for a given operational practice, the integrity of the cement sheath was shown to be less certain. Several factors contributed to this uncertainty. Firstly, the selection of caprock material and plasticity models for caprock stress analysis has significant implications for the risk of cement sheath damage. Secondly, the statistical distribution of caprock mechanical properties is typically quite broad through the overburden and caprock intervals, meaning that average zone mechanical properties may not be sufficient to model and design cement sheath integrity. Thirdly, it is necessary to adequately constrain our knowledge of the initial state of stress within the cement sheath after placement, and before steam injection. Our results show that these three factors can be adequately constrained to reduce well integrity uncertainty through the integration of geomechanical caprock integrity analyses and cement sheath integrity analyses. In this study we combine relatively time-consuming coupled finite element method analyses with rapid semi-analytical system response curve methods for cement sheath integrity. In so doing, we quantify the impact of the uncertainties present in caprock modeling and in the constitutive modeling of thermal cement blends on a risk-based evaluation of cement design requirements.
Abstract In recent years, a project was initiated to identify a safe and practical alternative to conventional silica-based cement slurries. The objective was to eliminate exposure to respirable crystalline silica (RCS) in oilfield cementing operations. RCS, as well as being linked to various respiratory illnesses (1), has now been identified as a human lung carcinogen (2), implying there is an established link between exposure to RCS and lung cancer. When cementing well sections with a bottomhole static temperature (BHST) of over 110°C [230°F], a cement powder containing silica flour must be used to ensure the set cement matrix is stabilized to be able to withstand persistent exposure to these temperatures over time (mitigating against strength retrogression). A certain proportion of the silica within these conventional cement blends is classified as RCS. The newly developed system, known as zero respirable crystalline silica blend or ‘ZRCS-blend’, was successfully applied on numerous occasions on a Norwegian rig. Interestingly, the system found successful application in a batch-drilled conductor campaign on a high-pressure/high-temperature (HPHT) field where the potential exposure during production exceeded 110°C [230°F]. Whilst being a safer alternative to conventional cement systems, the ZRCS-blend was able to deliver a top of cement (TOC) to the seabed on each and every occasion during the campaign, thus eliminating the need for any remedial operations. As shown by proven success of the ZRCS-blend offshore on the Norwegian continental shelf, the system provides an alternative to silica-based cement for operations worldwide, to comply with regulations and health, safety, and environmental guidelines.
Goenawan, Jessica (Schlumberger) | Goncalves, Rodrigo (Schlumberger) | Dooply, Mohammed (Schlumberger) | Pasteris, Mathieu (Schlumberger) | Heu, Tieng-Soon (Shell) | Chan, Lakmun (Shell) | Bhaskaran, Sunderesan (Shell) | Hinoul, Wim (Shell)
Abstract The well construction strategy for the Deepwater Malikai project, Malaysia, included 36-in. structural pipe jetting and 13 5/8-in. surface casing riserless cementing for top-hole sections with the objective for further development of lower sections with tension leg platform (TLP). Cementing of the 17 ½-in. surface hole mainly dominated by shale formation and penetrating multiple shallow faults required isolating shallow gas sands by bringing top of cement to the seabed, thus meeting the well integrity requirement stipulated by the Malaysian Petroleum Management (MPM). The cement slurry design for the 13 5/8-in. casing with riserless mud recovery system includes selection of lightweight trimodal particle-size distribution cement blend optimized with a gas migration control agent and low-temperature dispersant. This mitigates dynamic losses in unconsolidated formations and faults having narrow margins between pore and fracture pressures. Cement slurry achieves faster compressive strength and static gel strength development at lower seabed temperature, preventing casing subsidence and providing good shoe strength. The cement job design respects density and friction pressure hierarchies, providing flat fluid interfaces between successive fluids pumped, combined with optimal casing standoff and displacement efficiency ensuring effective mud removal in highly deviated large-annulus top-holes. This paper will discuss the extensive laboratory testing employed to qualify the engineered trimodal lightweight cement slurry design and effective mud removal strategy fit for the applications on the seven batch-set top-hole sections, achieving zonal isolation requirement.