Cement Slurry System Research Articles

Research on a New Latex Anti-Gas Channeling Cement Slurry System

It is one of the technical problems existing in the current cementing technology that gas channeling frequently occurs after the well cementation process. The new latex anti-gas channeling cement slurry system is put forward to solve this problem effectively and also filled up the domestic blank in this field. The study found that the new cement slurry system has the good ability of water loss control, liquidity and the thickening time can be adjusted. The static gel strength analysis and gas channeling simulation analysis shows that under the condition of high temperature, the anti-gas channeling has good effect. In addition, the sensitive factor experiment research shows that the cement slurry system has less affected by the site factors, so it has good application prospects.

Research of Nanosilica Particles Grafted with Functional Polymer Used as Fluid Loss Additive for Cementing under Ultra-High Temperature

On account of that the domestic polymer fluid loss additive exists some severe problems, such as, inferior thermal resistance, poor salt tolerance, strong shear-and thermal thinning behavior, a novel polymer/silica nanocomposite PADMO-V@NS is used as ultra-high temperature fluid loss control additive for cementing. In the present study PADMO-V@NS was prepared through an in situ free radical copolymerization of 2-acrylamico-2-methylpropane sulfonic acid (AMPS), N,N-dimethylacryl amide (DMAM), maleic anhydride (MA), octadecyl dimethylallyl ammonium chloride (ODAAC) and triethoxyvinylsilane (VTS) modified nanosilica. The linear hydrophobic associated copolymer was regarded as the shell and the modified nanosilica as the core. The microstructure, compositions and thermal resistance of PADMO-V@NS were investigated through FTIR and TGA techniques. The results showed that the copolymer modified with nanosilica particles possessed more excellent thermal stability than that of PADMO, and the most rapid decomposing temperature of PADMO-V@NS was highly up to 396.9°C. The application performance of PADMO-V@NS in cement slurry exhibited that it had excellent fluid loss control capacity, good high temperature resistance, strong salt tolerance and mild shear-/ thermal thinning performance, and could be used in 220°C and saturated brine circumstances. Moreover, comparing to PADMO, the compressive strength of set cement containing the copolymer increased over 20 % at 80°C, atmosphere pressure and curing time of 1 day due to the reaction of residual silanol groups with Ca (OH)2. The laboratory research results indicated that the multi-functional fluid loss additive composed of hydrophobic associated polymer/silica nanocomposite had bestowed on the cement slurry systems good comprehensive properties, and may have extensive applications in deep & ultra-deep oil/gas wells cementing.

Research on Low Density Cementing Technology of Coalbed Methane Well

The pressure of the coalbed methane (CBM) reservoir is relatively low, there is serious loss circulation, andlow mechanical strength of the coal, which seriously influence the cementing quality. In this paper, according to the characteristics of coal in southern Qinshui basin, an ultra-low density cement slurry system and a foamed cement slurry system are designed and developed to reduce the density of cement slurry by adding lightening admixture and foaming agent through the experimental method. An appropriate bridging type preflush system is also researched and developed. Considering the drilling conditions, the operation technologies are put forward.The ultra-low density cement slurry system has good rheological performance, small API filter loss (≤ 45 mL/ (30 min·6.9 MPa)), excellent sedimentation stability, suitable thickening time and higher early strength. Foamed cement slurry systemhas good rheological performance, excellent sedimentation stability andsuitable thickening time, and can satisfy the compressive strength requirements for the cementing of CBM wells. The fluid loss of the bridging type preflush system is small under the medium or high pressure, withgood rheological performance,andexcellent plugging ability. The ultra-low density cement slurry system and foamed cement slurry system were applied in 14 and 11 CBM wells respectively, and good results have been achieved.

Drilling Engineering Design of Well WT-1

Well WT-1 is a key exploratory well deployed at Jiangjin district of Chongqing for the exploration of shale gas reservoir with the design depth of 4,900.00 m and designed drilled strata at Ordovician Pagoda formation. Due to the complex situations in this area, there are some technical problems, for example, prediction accuracy of formation pressure is poor, Maokou formation is gas bearing formation with ultra-high pressure, and coal seam and shale bed are easy to collapse. Therefore, the well designing comprehensively adopted conventional casing program design methods, setting position design methods and safety risk assessment technique for casing program design; metal ion polymer drilling fluid system was designed in the upper part, and aluminum amine blocking anti-sloughing drilling fluid system was applied in the lower interval of interest. For well cementing design, conventional cement slurry system was used in the upper part and non-permeable latex channeling preventable slurry system was used in the lower part to improve the quality of cement-formation interface, and two special filter cake curing agents were also used in the design.

Application of Cementing Technology for Shale Gas Horizontal Well in Jiaoshiba Block of Fuling Area

In response to the difficulties happened during shale gas horizontal well cementation in shale reservoir of Jiaoshiba Long maxi group in Fuling, through continuous laboratory tests and analysis on site, this paper achieves the following research results: the method of enhancing cleaning efficiency by further improving ahead fluid system; the method of reducing the shrinkage of cement rock and improving anti-gas channeling ability of cement slurry by perfecting the cement slurry system; method of strengthening the supervision of the placement of centralizers by placing the centralizers reasonably; water substitution method with large flow rate of whole well. All these methods form a comprehensive technology, which is applied in 7 wells, such as JY 29-4HF, JY 8-1HF, and JY 15-2HF and so on. All the cement evaluations are great, which indicates that the comprehensive technology is suitable for shale gas horizontal well cementation in Jiaoshiba.

Laboratory Study on Optimization of Oil-Soluble Cement Material

A new cement slurry system with strong selective permeability to oil and water, namely oil-soluble cement system, was introduced. It is composed of three kinds of basic agents including pore-enhancing grains, pore-connecting agent and phase-permeability enhancing agent. The pore enhancing grains-ZKJ-1, which can broaden the pore significantly was obtained from many natural oil soluble organics. In order to further interconnect the cement stones’ pores and enhance the selective permeability to oil and water, the YRJ was selected as the connecting agent and phase-permeability enhancing agent. Combined with three other agents, the cement slurry has a good selective permeability to water and oil and high strength. Key words : Oil solubility; Cement additive; Effective permeability; Laboratory testing

Laboratory Study on the Polymer Flexible Cement Slurry System

A polymer flexible cement slurry system has been developed because cement stone has poor deformability and can be destroyed easily in complex underground conditions and the subsequent construction of wells. A lot of laboratory experiments has been done to evaluate the properties of this slurry system and the emphasis was put on the properties of cement stone such as compressive strength, flexural strength, corrosion resistance and volume shrinkage. The result of study indicated, this polymer flexible slurry cement system had properties of resisting high temperature, salt endurance, low fluid loss, zero free liquid, the thickening curve emerged right angle with short transition period and anti-gas channeling. The compression strength of the cement stone was high, plasticity was strengthened, permeability was low, it was good to able to bear corrosion. Key words : Oil well cement; Strength of cement; Flexibility of cement; Resistance to corrosion

Study on Cement Slurry System for Deep and Ultra-Deep Wells

Cementing quality can’t meet the requirements in deep and ultra-deep wells cementing because of many factors such as long open hole section, multiple pressure system, high temperature and high pressure. In order to solve the problem of cementing in deep and ultra-deep wells, retarder and fluid loss additive were studied, then the cement slurry system for deep and ultra-deep wells were developed and the performance was evaluated. The results show that the cement slurry has steady performance for high temperature, adjustable thickening time, less fluid loss, good settlement stability, and high compressive strength, all of which can meet the requirement of cementing in deep and ultra-deep wells. Pilot tests of this cement system were conducted in more than 30 wells in Shengli, Dagang, Liaohe, Jiangsu, Jilin and Offshore oilfield, cementing qualities of these wells were qualified, which indicates that comprehensive performance of this kind of cement slurry system can meet the technical requirements for deep and ultra-deep wells cementing, which provides the references for the deep and ultra-deep wells cementing in all of the word. Key words : Deep and ultra-deep wells; Cementing; Fluid loss additive; Retarder; Thickening time

The Application of Fiber Cement Slurry Used to Prevent and Block Leak

Aimed at the cement slurry leak problem in the leakiness area cementing of Jilin oilfield, the fiber cement slurry system was developed. The general performance of fiber cement slurry, such as the pressure strength, thickness time, filter loss, flowing ability and water separate rate, etc was analysis in the room condition. The preventing and block leak ability was evaluated. The room and field tests prove that the ability of the fiber cement slurry is best. It can make the field cementing requirement in the leakiness formation and has the best effect of preventing and block leak ability.

Technology for Improving Life of Thermal Recovery Well Casing

In steam injection process, casing is heated by steam, the change of casing temperature produces thermal stresses in the casing, the casing deforms when stresses exceed the yield point of its material. Casing failure is becoming increasingly prominent in thermal recovery wells, which severely restricts the development effect of such reservoirs, improving casing life of thermal recovery well has become a urgent problem to be solved. Through on-site survey and analysis, reasons for casing damage were determined as follows: strength change by high temperature, sand flow over of oil formation, poor cementing, unfavorable heat insulation and bad material for casing. In order to improve casing life, the supporting measures are introduced, the measures include pre-stress cementing technology, using casing head, thermal stress compensator, high-performance insulation tubing, high temperature cement slurry system, FRT110H special casing, and early sand control completion technology. Field application of these measures has gotten better effect in Shengli oilfield in recent years, the damage rate of thermal recovery well has decreased obviously, and this can provide reference for the efficient development of similar reservoirs at home and abroad. Key words : Casing failure; Thermal recovery wells; Special casing; Cementing; Sand control completion

Cementing Leakproof Research and Application in JiLin HaiTuoZi Exploration Area

A long period of development in Haituozi exploration area, downhole conditions are constantly changing, increasingly complex, and the original cementing technology is difficult to solve the region's low pressure leakage problems. For the special circumstances of the region, we set up a special research team, focus on starting from the the preferred cement slurry system, and improve stability, toughness, plugging, leak-proof ability of the slurry system performance; Another optimization cementing design and perfect cementing supporting measures effectively solve the region's dropout problem.

The Research of Cement Slurry System for High Angle Holes in Fuyu Area

In this paper, aiming at the Fuyu high angle holes cementing technical issues, in-depth study the quick-setting, high early strength and micro-expansion anti-channeling slurry system. Use this system in Fuyu region high angle holes cementing engineering, the completion of 10 high angle holes were all qualified, 8 of which were quality well, the pass rate of 100% and quality rate of 80%.Solve the difficult problem of the cementation quality and packer formation of the cement sheath, ensure the cementing Quality of Fuyu city high angle wells, which has an important guide and reference on Jilin Oilfield in the future development of the deep horizontal and cementing technology.

Experimental and Theoretical Study on Slag MTC Improving the Cementing Quality of the Second Interface

In view of the complicated issue that how to improve the cementing quality of the second interface in cementing engineering, experimental and theoretical research on slag MTC slurry improving the quality of the second interface was carried out in the paper. Experimental study shows that slag MTC and mud cake can achieve overall cementing; the volume shrinkage ratio of slag MTC is far less than the cement slurry system; and the strength of slag MTC cannot be affected by the presence of mud cake and is greater than low-density cement slurry. Theoretical analysis shows that the alkali activator and Ca(OH)2 produced by hydration can react with SiO2 which exists in mud cake and dead mud to get C-S-H gel with a low ratio of calcium to silicon, and improving the quality of the second interface. The study on the chemical shrinkage ratio of the products of slag MTC hydration was made by using the method of chemical analysis, and low-shrinkage mechanism of MTC was revealed. The results show that mud cake solidification, dead mud solidification and low-shrinkage ratio are fundamental to improve the cementing quality of slag MTC and formation.

Study on New Cement Slurry System for Heavy Crude Oil Thermal Recovery in Well Cementation

The multi-cycle recovery of heavy crude oil thermal by steam injection and stimulation has serious effects on the integrity of cementing sheath. At present, the class G oil well cement with silica sands, less resistant to high temperatures, does not meet the quality of the heavy crude oil well cementation and requirements of recovery and production. The laboratory results show that Aluminates cement has the characteristics of high early strength; meanwhile, it can maintain strength and stability in a long-term under the circulation of high and low temperature conditions. However, its hydration product C3AH6, which makes it a sharp recession in intensity at low temperature, limits its application. According to the clinker selection and compounding with the main item of Aluminates cement indoor experimentation, there comes out a new type of cement binder which generates C3ASH4 and other stable phase within rounds of high and low temperature cueing, and made the crystal structure of cement in dense arrangement. With this method, cement hydration structure can be maintained with a long-term stability; and it has the value of further development.

Technical Principle of Integrated Solidification and Cementation at Cement-Formation Interface with Mud Cake to Agglomerated Cake (MTA) Method and its Oilfield Application

The technical principle of integrated solidification and cementation at cement-formation interface (ISCCFI) with Mud Cake to Agglomerated Cake (MTA) method based on the mud cake modifier and forming agent of agglomerated cake can be divided into two steps. Firstly, add the mud cake modifier (the amount is 1 % to 3 %) to the drilling fluid before drilling the isolation section, and keep this proportion until the well completion. Secondly, prepare 3 to 4 cubic meters of prepad fluid based on forming agent of agglomerated cake before the well cementing operation. This new method doesn’t need to change oilwell cement slurry system. In order to verify the practical cementing effect of MTA method, it was applicated in 16 adjustment wells (9 conventional wells and 7 heavy oil wells) in the old area of two oilfields in China. The interpretation results of CBL/VDL (Cement Bond Logging/Acoustic Variable Density logging) show that the qualified rate of casing-cement interface and cement-formation interface is up to 100 %, and the qualified rate of cement-formation interface increased by 30 % in Shengli oilfield and the average high-quality rate of all the isolation section length at cement-formation interface reaches 90.48 % in Henan oilfield.

The Influences of Interface Missing and Formation Property on Shearing Strength at Cement–Formation Interface

The thin interlayer channeling induced by the shear failure at the cement–formation interface due to the fracturing operation is one of the bottlenecks for efficient development in low-permeability oilfields. Therefore, the influence laws of interface missing and formation property on the shearing strength at the cement–formation interface are studied according to the simulated experimental system (including preparation of simulated wellbores based on physical properties and compaction law of formation, mud cake formation, samples maintenance, strength test, etc.) established based on the drilling fluid sample and cement slurry system obtained from Daqing oilfield, China. The experiments showed that interface missing and formation property have a very close and complex realationship with the shearing strength at the cement–formation interface. When the quantity of interface missing is less than 10%, it has no obvious effect on the shearing strength at the cement–formation interface, whereas if the quantity of interface missing is greater than 10%, the shearing strengh at the cement–formation interface is inversely proportional to the amount of interface missing. The shearing strength at the cement–formation interface is inversely proportional to the amount of formation permeability.

Research and Practice on Cement Slurry of Oil and Gas Reservoir Protection

Based on the reservoir characteristics of Turpan-Hami (TH) oilfield and the damage mechanism of the cement slurry to reservoir, and in combination with the cementing features of different wells and their requirements on cement slurry performances, cement additives are optimized for reservoir protection. These are fluid-loss additives that contain macromolecule material, dispersant composed of polycondensated sulfides, gas channeling inhibitor of fine aluminum, fluid retardant, and so forth. Optimized cement slurry systems greatly improve the cementing quality, minimize the formation damage, and protect oil and gas reservoirs.

Different Methods To Avoid Annular Pressure Buildup by Appropriate Engineered Sealant and Applying Best Practices (Cementing and Drilling)

Summary Many wells that have been successfully cemented initially are showing annulus pressure buildup because of damaged cement- sheath integrity by post-cementing operations/conditions. This has been a concern by many operators where wellbores may be exposed to severe conditions and/or production regimes over a period of time. Sometimes this problem can be temporarily dealt with by releasing the annulus pressure, if environmental conditions and well type will allow. However, this method of annular gas production relief is not a long-term solution to the problem. In addition, it is not always possible to reduce the annulus pressure by releasing the trapped pressure into the environment on a regular basis, even if all other conditions permit this operation. An engineered cement-slurry system can save the operator from facing this situation by applying a lifetime zonal isolation remedy through the proper cement job design. Gas injection in specific areas in the UAE is performed to help maximize the production from these development fields. This paper will discuss the process of engineering a cementing system for these gas-injection wells and the development of a solution that has successfully protected wellbores in gas-injection areas where high pressures are applied to the wellbore. By treating the cement under defined wellbore conditions and studying the mechanical behavior of the cement sheath, it was possible to design a cement- slurry system that could withstand the high pressures applied through gas-injection operations. The mechanical behavior was evaluated using 3D finite element analysis (FEA) that considers mechanical properties such as Young's modulus, Poisson's ratio, and tensile strength in addition to confined compressive strength. The importance of complete zonal isolation is of high order. Elastic cement designs have provided a resilient nonfoamed, or conventional, system that successfully isolated the wellbores for more than a dozen gas-injection wells.

Thermal Sealants Improve Cementing in SAGD Areas

Abstract With the high demand for oil and gas, operators are becoming increasingly interested in unconventional sources of hydrocarbon. One of the major sources in the world is heavy oil, which has been defined by the API as oil that has API gravity of less than 22.3 °API at 15.6 °C (60 °F) (extra heavy oil, or bitumen, has 10 °API or less). Because heavy oil does not flow on its own in the wellbore, a mechanism must be used to recover the oil by making it mobile. Among the different experimental and operational methods, steam-assisted gravity drainage (SAGD) has been the method of choice for the past few decades. This process uses steam to heat the immobile oil and reduce its viscosity so it can be extracted, usually by using pump jacks. These heavy oil wellbores need to be zonally isolated to help ensure that the reserves are produced properly without environmental or production optimization challenges. In Alberta and Saskatchewan, many wells are drilled and cemented in designated heavy oil fields where SAGD is applied to stimulate production. Most of these wells are successfully cemented, however, some wells experience zonal isolation failures that result in steam breakout or steam loss into non-targeted zones. While the problem may be related to the primary cement job, it may also have been created by post-cementing operations and/or conditions. Sometimes the problem may be temporarily solved by conventional methods, however, the ultimate remedy may have to be applied eventually. The long-term integrity of the cement sheath behind the casing should be planned with drilling, completion, production/injection and abandonment stages considered. A properly designed and engineered cement slurry system can help save a wellbore/field from additional unplanned expenses. The process is shown below:Cement slurries are designed under defined wellbore conditions and exposed to field conditions in the laboratory.The mechanical behaviour of the cement sheath under downhole conditions is studied using three-dimensional, finite element analysis software.The endurance of the cement sheath under applied conditions is predicted and optimized.Operation and placement of the selected slurry is studied to help ensure optimum execution. Stresses exerted on the cement sheath from wellbore operations during construction, injection or production that could damage the cement sheath are integral to the study. These conditions are analyzed to help engineers understand the post-cementing operational effects on the sealant system. This paper presents the design criteria for finding the fit-for-purpose sealant systems that can successfully protect wellbores under harsh environmental conditions of SAGD and cyclic steam stimulation (CSS) operations. Introduction The long-term integrity of a cement sheath throughout a well's life is the ultimate factor for determining whether the sealant will withstand the planned operations, production and injection that are planned for the well. In the case of heavy oil operations, the primary design considerations for a long-lasting sealant are the temperature and pressure regimes. The stresses caused by the extreme changes are exerted on casing, cement and the rock.

Cement slurry system for controlling external casing corrosion opposite fractured and vugular formations saturated with corrosive water

The results of tests carried out to develop a durable corrosion-inhibiting cement blend for use in the annulus between casing and surrounding formation are described. The blend was tested in the laboratory under corrosive conditions of typical Saudi Arabian fractured vugular formations saturated with highly corrosive water. The high chloride and sulfate ion contents present in the formation water have resulted in loss of strength and sloughing of the casing cement, thus leading to increased corrosion and pitting on the outer casing surface and consequent leaks. API class cements and their derivative blends are usually specified for improved sulfate resistance. Such cements, however, do not afford adequate protection of the casing against corrosive environments. The new cement blend presented in this work is a pozzolan blended portland cement which is composed of ultrafine particles having a C3A (tricalcium aluminate) content of 8–12%. The ultrafine particles hydrate to form a cement with a markedly reduced permeability, thus creating a barrier which decreases the amount of corrosive formation water reaching the casing. The high C3A content, in turn, provides enough aluminate to lock the corrosive elements into an insoluble compound, preventing them from reaching the casing and thus inhibiting corrosion. Furthermore, the ultrafine particle size of the cement, with a higher C2S (dicalcium silicate) to C3S (tricalcium silicate) ratio, and the presence of pozzolan afford a stronger cement of low permeability which is more durable and less susceptible to sulfate attack.