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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.
In this approach, the solid is a dryblend slurries with low porosity, good mixability, slurries has resulted in systems cement, while the porosity of the and good rheology. Optimized dry blends that can successfully isolate long sections slurry is the volume of liquid divided by the have a specific gravity ranging from 1.55 of openhole. One of the (for 10.5-lbm/gal slurry) to 2 (for 13-slurries prevent losses into weak formations major changes introduced by this method lbm/gal slurry). The broad range of densities and can eliminate the need for is that the specific gravity of the dry blend that can be covered shows clearly the lead/tail slurries and multistage cement is systematically deducted from the design flexibility arising from this new jobs. High early-compressive strengths required slurry density for a given porosity.
Abstract The production of hydrocarbons from pressure-depleted zones is becoming a common practice around the world and drives the constant development and improvement of cementing technology. This paper addresses the evolution of lightweight cement slurries to ensure zonal isolation and mechanical stability of casing in highly permeable and depleted formations. To prevent lost circulation while cementing depleted formations, a new technique has been developed based on adding inert fibers to ultralightweight slurries. During the cementing operation, the fibers create a network across the loss zone, to enable the cement to bridge off these zones and regain circulation. Also, these fibers enhance the mechanical properties of the cement as the created net provides additional stability to resist tensile stresses. This paper discusses the challenges and solutions of developing ultralightweight slurries (without foaming) that control rheology and cement properties by the interaction of fibers and cement particle size distribution. The paper addresses the synergies that cement slurries and inert fibers, with specific gravity values between 1.0 sg and 0.88 sg, bring to cement production casings in the Cantarell field of Mexico. The pay zone of the Cantarell field is a highly fractured, highly permeable, vuggy, and depleted Cretaceous formation that is typically drilled under total loss of circulation. The ability to reduce and prevent losses of slurry by adding this engineered fiber helps to ensure that the cement slurry is placed according to design to provide good zonal isolation and to permit completion of the new well. Introduction The design of the primary cementing job in the Cantarell field has been a continuous challenge to achieve a good zonal isolation along a Cretaceous formation which is considered the main producing horizon for Mexico in terms of barrels of oil produced per day. Cantarell field (Fig. 1) is the second largest producing field in the world behind Ghawar field in Saudi Arabia and was discovered in 1976. The upper reservoir is an uppermost Cretaceous brecciated dolomite, and the lowest stratigraphic reservoir in the field is a lower Cretaceous dolomitic limestone. The field is made up of a number of subfields or fault blocks, which geologically are in an overthrust structural setting. The subfields are: Akal, Chac, Kutz, and Nohoch. The field reached an early peak in production of 1.1 million B/D in April of 1981 from 40 oil wells; however, in 1994, the production was down to 890,000 B/D. One year later, in 1995, it was producing 1 million B/D because the Mexican government decided to invest in that field to raise the production level. To reach that level, the local operator built 26 new platforms, drilled many new wells, and built the largest nitrogen extraction facility capable of injecting a billion ft3/D of nitrogen to maintain reservoir pressure. Consequently, they were able to raise the oil production rate in 2001 to 2.2 million B/D. Today, the field produces 2.1 million barrels. On the other hand, analysis indicates that the gas located at the upper section of the formation zone will continue to progress in Cantarell as a result of hydrocarbon production. Thus, currently producing wells will stop producing in the future. The pace at which production will decrease will depend on the number of wells that continue to produce. Therefore, included in the stated goals for the project, based on the reservoir management policies, is the maintenance of pressure by injecting nitrogen and the closure of wells with high gas/oil ratio.
New lightweight cement technology, based on increased cement fineness, has been developed in response to problems associated with cementing primary oilfield casings in cold environments. When low density slurries are required at low temperature conditions, adequate compressive strengths may be difficult to obtain. The new technology presented in this paper, called ultrafine cement, offers lightweight cement slurries paper, called ultrafine cement, offers lightweight cement slurries (10.0 lb/gal-13.0 lb/gal) which exhibit much higher early compressive strengths than conventional lightweight systems when cured in cold environments (40 deg. F - 80 deg. F).
By means of laboratory investigation, this paper introduces ultrafine cement as a unique lightweight primary cementing material. Performance properties of ultrafine slurries are discussed and comparisons to commonly used lightweight cements are presented.
Cementing oilfield casings in cold environments has been a challenge to field operators for many years. The in capability of cement slurries to gain early compressive strengths in these operations has led to increased research efforts and development of various types of accelerated cement compositions. Low temperature cement designs and proper cementing techniques, from the permafrost of the Alaskan North Slope to the cold waters of offshore exploration, have been documented extensively. Few papers, however, have been written on the performance of lightweight cement slurries in cold environments because very few lightweight cement slurries are available which can perform under low temperature conditions.
Recent advancements in particle size technology, however, have yielded a new ultrafine cement that performs with exceptional results at low temperatures. Tested in the laboratory from 40 deg. F to 80 deg. F, ultrafine cement slurries exhibit early compressive strengths more rapidly than conventional lightweight slurries of equal density.
Ultrafine cement technology was introduced initially to oilfield operations for remedial cementing. While use in this area continues to grow, refinement of the cement in both its physical and chemical properties has resulted in particle sizes physical and chemical properties has resulted in particle sizes that are 10 times smaller than standard oilfield cements. Increased surface area, requiring significantly more water, results in a low density mix, ideal for use in lightweight primary cementing applications.
The advantages of ultrafine cement for primary uses include less waiting-on-cement (WOC) time, a stronger cement sheath during drillout, simple slurry design - (cement and water), and other secondary benefits.
A detailed discussion of the properties and applications of ultrafine cement for primary cementing are presented in this paper. Also presented is a review of lightweight cement paper. Also presented is a review of lightweight cement compositions currently used in cold environments, including performance comparisons to ultrafine cement. performance comparisons to ultrafine cement.
Lightweight cements play a vital role in primary cementing operations. A prime reason for the use of lightweight cement is the reduction of hydrostatic pressure when cementing across a weak formation. Other uses for lightweight slurries include preventing lost circulation during pumping operations, preventing lost circulation during pumping operations, eliminating "fallback" after the cement is placed, cementing long annular columns, or as a "filler" cement to lower costs.
Today’s North American land drilling and cementing are facing new challenges due to increased hydrocarbon extraction, especially in the Permian basin. For instance, operators in the region frequently face severe losses during drilling or cementing, which are not prevalent in the other US basins. Lost circulation is a major problem that increases well construction costs and time as well as delays well completion and production in a market where efficiency and costs are the main drivers.
Solutions to this perennial problem include two-stage cementing, contingency liners, and use of lightweight cement systems. Lightweight cement reduces hydrostatic pressure to prevent losses particularly in weak formations. Typically, lightweight cements are designed by incorporating expensive micro spheres and/or foam. These designs are relatively costly compared to conventional technologies, and they involve operational complexity in the field. There are other cost-effective materials that allow for designing lower density cements, which have pozzolanic reactivity to increase strength of the set cement. But these traditional materials cannot provide enough compressive strength in the 10.3 ppg to 11.5 ppg density range.
In this paper, several case histories will be presented from more than 100 jobs pumped to date. The selected job(s) will be explained with real-time acquisition data, and these data will be compared to pre/post-job computer simulations to explain the dynamics of the placement. Numerous field applications of the novel and cost-effective non-beaded lightweight cementing technology will be described. The new lightweight has a lower hydrostatic pressure during pumping, hence preventing the occurrence of lost circulation. It also delivers superior strength after cement setting, thereby providing better zonal isolation and mechanical support to the casing. Because of its efficient delivery utilizing the same equipment, processes and personnel, this new cementing technology is easily integrated into the current field operations.
The novel contribution to the industry is the successful field application of a non-beaded lightweight low permeability cement to more than 100 jobs. This lightweight cement is uniquely formulated with a new unconventional micromaterial that provides superior strength performance, improved operational efficiency, and safety combined with better economics over beaded or foamed cement system. Based on multiple jobs that were completed, this innovative lightweight cement has successfully mitigated losses, thus maintaining lower equivalent circulating densities to achieve the required top of cement. It also eliminated the need for multiple cementing stages, thereby enabling faster well completion and dramatically reducing well construction costs.