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Two forms of derivatized cellulose have been found useful in well-cementing applications. The usefulness of the two materials depends on their retardational character and thermal stability limits. This is commonly used at temperatures up to approximately 82 C (180 F) for fluid-loss control, and may be used at temperatures up to approximately 110 C (230 F) BHCT, depending on the co-additives used and slurry viscosity limitations. Above 110 C (230 F), HEC is not thermally stable. HEC is typically used at a concentration of 0.4 to 3.0% by weight of cement (BWOC), densities ranging from 16.0 to 11.0 lbm/gal, and temperatures ranging from 27 to 66 C (80 to 150 F) BHCT to achieve a fluid loss of less than 100 cm3 /30 min.
This page provides a brief review of illustrative field applications of polymer waterflooding as reported in the literature. In 1983, Manning et al. published a comprehensive and classic summary of the field results and performance of more than 250 polymer waterflooding projects and provided information relating to the early field applications of polymer waterflooding. Figure 1 shows the incremental oil production response for the North Burbank polymer flood. A polymer waterflooding project that involved a large full-field flooding project at the North Oregon Basin field in Wyoming's mature Big Horn Basin oil-producing area was reported in 1986 to be producing 2,550 BOPD of incremental oil production. It was reported that this polymer flooding project would recover ultimately more than 10 million bbl of incremental reserves from the mature North Oregon Basin field. The field project involved the flooding of both a fractured carbonate formation and a fractured sandstone formation with a polymer flood using partially hydrolyzed polyacrylamide(HPAM).
This article describes the chemical make-up and application of the types of gels most commonly used in conformance improvement. It also discusses the ways in which these gels can be classified. Oilfield conformance improvement gels come in a wide range of forms and chemistries. Table 1 provides an overview of various conformance improvement gels. CC/AP gels have an exceptionally robust gel chemistry and are highly insensitive to oilfield and reservoir interferences and environments.
Early application of polymers for use during oilfield conformance improvement operations was focused on improving volumetric sweep efficiency of waterfloods. More recently, polymers have been used extensively in disproportionate permeability reduction (DPR) and relative permeability modification (RPM) treatments for water shutoff and in conformance improvement polymer-gel treatments. This page discusses polymers used in oilfield operations and how they contribute to conformance improvement. Polymers are large molecules and chemical entities referred to as macromolecules. Polymer molecules are the resultant chemical specie when a large number of relatively small and repeating molecular entities, called monomers, are joined together chemically.
Disproportionate permeability reduction (DPR) is a phenomenon whereby many water-soluble polymers and many polymer gels reduce the permeability to water flow to a greater extent than to oil or gas flow. DPR is also referred to as relative permeability modification (RPM). In Disproportionate permeability reduction, a review is presented of the concepts, applicability, limitations, and desirability of the DPR phenomenon as it applies to conformance improvement water-shutoff (and/or water-reduction) treatments. This article focuses specifically on polymer use for DPR and RPM. As early as 1964, certain polymer flood water soluble polymers were known to impart DPR to water flow in reservoir rock that had been previously flooded with the polymer.
When conducting a polymer waterflood, a high-molecular-weight and viscosity-enhancing polymer is added to the water of the waterflood to decrease the mobility of the flood water and, as a consequence, improve the sweep efficiency of the waterflood (See Polymer waterflooding). This articles focuses on the design and field implementation of a polymer waterflood. Working up a flood design is one of the first steps when implementing a polymer-waterflooding project. When selecting a polymer for a polymer waterflooding project, one should try to maximize, as best as possible, all the following polymer attributes. The optimum concentration of the polymer to be injected is a critical parameter in the design of an effective polymer waterflooding project.
Fluid-Loss-Control Additives (FLAs) are used to maintain a consistent fluid volume within a cement slurry to ensure that the slurry performance properties remain within an acceptable range. The variability of each of these parameters (slurry performance properties) is dependent upon the water content of the slurry. If the water content is less than intended, the opposite will normally occur. The magnitude of change is directly related to the amount of fluid lost from the slurry. Because predictability of performance is typically the most important parameter in a cementing operation, considerable attention has been paid to mechanical control of slurry density during the mixing of the slurry to assure reproducibility.
John, Blevins (Hibernia Resources) | Van Domelen, Mark (Downhole Chemical Solutions) | West, Zach (Downhole Chemical Solutions) | Rall, Jason (Downhole Chemical Solutions) | Wakefield, Drake (Downhole Chemical Solutions)
Abstract Since the early development of unconventional resource plays, slickwater fracturing fluids have expanded rapidly and are now the most common type of fluid system used in the industry. Slickwater and viscosifying friction reducer (VFR) fluids consist of polyacrylamide (PAM) polymers and are typically delivered to location in a liquid form such as a suspension or emulsion in a hydrocarbon-based carrier fluid. Recently, advances in dry powder delivery operations have provided unique advantages over the liquid versions of FRs including cost savings and improved health, safety and environmental (HSE) aspects. This paper describes the dry powder delivery process and describes the advantages that this new technology has brought to field operations. The method involves delivering polyacrylamide powder for slickwater fracturing treatments directly into the source water on location, thereby eliminating the use of liquid polymer slurries or emulsions. Liquid friction reducers typically contain 20-30% active polymer loading, with the remaining volume being the carrier fluid to keep the polymer in suspension. By delivering 100% powder, several benefits are gained including elimination of truck deliveries of FR liquids to location, reduction of total chemical volumes by 70-80%, reduction of spill hazards, and lower overall chemical costs. Different powders are available for various applications including the use of fresh or produced water, and viscosifying or non-viscosifying polymers. The key technology for "dry on the fly" (DOTF) operations is the powder delivery equipment. Due to the different molecular structures between polyacrylamide and guar polymers, delivering PAM is more technically challenging than guar and requires much higher mixing energy to achieve proper dispersion and hydration. The delivery system described in this paper uses a unique technology which creates the necessary conditions for powder mixing and has been successfully applied on over 350 wells since early 2019, with over 7,000 tons of polymer delivered.
Abstract As our industry is tapping into tighter carbonate reservoirs than in the past, completion techniques need to be improved to stimulate the low-permeability carbonate formation. Multistage acid fracturing technique has been developed in recent years and proved to be successful in some carbonate reservoirs. A multistage acid fracturing job is to perform several stages of acid fracturing along a horizontal well. The goal of acid fracturing operations is to create enough fracture roughness through differential acid etching on fracture walls such that the acid fracture can keep open and sustain a high enough acid fracture conductivity under the closure stress. In multistage acid fracturing treatments, acid flow is in a radial flow scenario and the acid etching process can be different from acid fracturing in vertical wells. In order to accurately predict the acid-fracture conductivity, a detailed description of the rough acid-fracture surfaces is required. In this paper, we developed a 3D acid transport model to compute the geometry of acid fracture for multistage acid fracturing treatments. The developed model couples the acid fluid flow, reactive transport and rock dissolution in the fracture. We also included acid viscous fingering in our model since viscous fingering mechanism is commonly applied in multistage acid fracturing to achieve non-uniform acid etching. Our simulation results reproduced the acid viscous fingering phenomenon observed from experiments in the literature. During the process of acid viscous fingering, high-conductivity channels developed in the fingering regions. We modeled the acid etching process in multistage acid fracturing treatments and compared it with acid fracturing treatments in vertical wells. We found that due to the radial flow effect, it is more difficult to achieve non-uniform acid etching in multistage acid fracturing treatments than in vertical wells. We investigated the effects of perforation design and pad fluid viscosity on multistage acid fracturing treatments. We need to have an adequate number of perforations in order to develop non-uniform acid etching. We found that a higher viscosity pad fluid helps acid to penetrate deeper in the fracture and result in a longer and narrower etched channel.
Wang, Chengwen (China University of Petroleum (East China), Shandong Key Laboratory of Oilfield Chemistry (Corresponding author) | Chen, Zehua (email: firstname.lastname@example.org)) | Chen, Erding (China University of Petroleum (East China) (Corresponding author) | Liu, Junyi (email: email@example.com)) | Xiao, Fengfeng (Drilling Technology Research Institute of Shengli Petroleum Engineering Corporation Limited) | Zhao, Hongxiang (Drilling Technology Research Institute of Shengli Petroleum Engineering Corporation Limited)
Summary Removal of useless and submicrometer-sized solids from drilling fluid, which exert significant effects on drilling performance, is a crucial part of sustainable and eco-friendly circulation in drilling operations. However, current solid-control methods for drilling-fluid reuse and recirculation, such as electronic-adsorption and chemical-flocculation methods, are associated with high cost and low efficiency and/or pollution of drilling fluid. In this study, a novel method using ultrasonic waves has been proposed to remove unwanted submicrometersized solids from polysulfonate drilling fluids. The results show that the suspension stability, viscosity, and particle size can all be significantly reduced, while the solid-separation ratio of the drilling fluid can be greatly enhanced by ultrasonic-wave treatment. The parameters of ultrasonic waves are optimized to be power of 3 kW, treating time of 30 minutes, treating frequency of 20 kHz, and ventilation (i.e., air) for 5 minutes in a laboratory scale. The scanning electron microscope (SEM) analysis shows that solid particles exhibit more obvious crystal morphology after ultrasonic-wave treatment, indicating that the breaking of gel-structure of drilling fluid due to the cavitation, mechanical, and heat effects of ultrasonic waves is the main mechanism for decreasing the suspension stability. Thus, the proposed ultrasonicassisted technique has a high potential for removing undesirable solids from drilling fluid and fulfilling its recirculation in a cost-effective and environmentally friendly manner. This new technology has been successively applied to 12 wells, and good results were obtained. Introduction The drilling fluid is known as the blood of the drilling operation, and it plays a vital role in balancing formation pressure, carrying and suspending drilling cuttings, transmitting water power, lubricating the drillstring, and keeping the drillbit cool and clean.