Proppant Type Research Articles

Field-Scale Experimental Study on the Perforation Erosion in Horizontal Wellbore under Real Fracturing Conditions

Limited-entry fracturing (LEF) technology is a widely used method to realize the simultaneous propagation of multiple fractures in horizontal wells. The key of this technology is to create high perforation friction to maintain the high treatment pressure in the wellbore and realize the uniform fluid entry of multi-fractures; however, high perforation friction cannot be effectively maintained due to the serious perforation erosion effect. Considering that the current laboratory studies mostly used small fluid injection flowrate, low injection pressure, and small proppant dosage, this study has developed a field-scale flow system to investigate the effect of various factors on perforation erosion under real field conditions. The filed-scale flow system uses the real fracturing trucks, proppant, and perforated wellbore, the fluid flow rate through perforation could reach 200 m/s and the injection pressure could reach 105 MPa. The effects of different parameters, such as injection flow rates, proppant concentration, proppant type, proppant size, and carrying fluid viscosity, on the perforation erosion were investigated. The experimental results show that: (1) The perforation friction during erosion goes through two stages, i.e., the roundness erosion stage and the diameter erosion stage. The reduction of perforating friction mainly occurred in the first stage, which was completed after injecting 1 m3 proppant. (2) After erosion, the perforation changes from the original circular shape to a trumpet shape, the inner diameter is much larger than the outer diameter. (3) The more serious perforation erosion is caused by the conditions of high injection flow rate, large proppant size, using ceramic proppant, and low viscosity fluid. The findings of this study can help for a better understanding of perforation erosion during the limited-entry fracturing in the horizontal wells, and also could promote the establishment of a theoretical model of perforation erosion under the field-scale conditions.

Mathematical model of linear and non-linear proppant concentration increase during hydraulic fracturing – a solution for sequential injection of a number of proppant types

It is known that much of the technology aimed at intensifying fluid inflow by means of hydraulic fracturing involves the use of proppant. In order to transport and position grains in the fracture, a uniform supply of proppant with a given concentration into the fracturing fluid is ensured. The aim of the operation is to eliminate the occurrence of distortions in the injection program of proppant HF. A mathematically accurate linear increase of concentration under given conditions is possible only if the transient concentration is correctly defined. The proposed approach allows to correctly form a proppant HF work program for both linear and non-linear increase in proppant concentration. The scientific novelty of the work lies in application of a new mathematical model for direct calculation of injection program parameters, previously determined by trial and error method. A mathematical model of linear and non-linear increase of proppant concentration during HF was developed. For the first time, an analytical solution is presented that allows direct calculation of parameters of the main HF stages, including transient concentrations for given masses of the various types of proppant. The application of the mathematical model in formation of a treatment plan allows maintaining correct proppant mass distribution by fractions, which facilitates implementation of information and analytical systems, data transfer directly from a work program into databases. It is suggested to improve spreadsheet forms used in production, which would allow applying mathematical model of work program formation at each HF process without additional labour costs. The obtained mathematical model can be used to improve the software applied in the design, modelling and engineering support of HF processes.

Application of the effective diameters of porous media to the non-Darcy flow analyses

Non-Darcy flows are a vital event leading to the inaccuracy in flow performance evaluation, particularly in the fractured wells in shale gas and tight oil deposits. The internal flow commonly indicates high flow rates at the early period of production, owing to the large geometric size of hydraulic fracture and high porosity in proppant packs. After that, the production flow rate decays steeply until the Darcy flow regime is attained. Therefore, accurate porous flow analyses from the Darcy to Forchheimer and then turbulent flow regimes are essential for optimal facility designs and economic productions in the unconventional deposits. The Comiti capillary model is recognised as the leading non-Darcy flow correlation for simple packed beds comprising mono-size grains. However, in actual hydraulic fractures, various types of proppants are used simultaneously and generally combined with numerous soil grains of different sizes and shapes. In this study, the Comiti model is modified by incorporating the effective diameters of the porous media and then examined for mixed complex multi-size packs. Subsequently, a novel type of non-Darcy flow equation is presented according to the logarithmic turbulent friction factor based on the physical variables determined only in the Darcy flow regime. The new equation presents accurate results for all the types of proppant packs under wide porosity and permeability ranges. The generalised non-Darcy flow correlation, which can be extensively employed from the Darcy to non-Darcy flow analyses, particularly beyond the Forchheimer regime, is presented for the accurate flow evaluation of the fractured reservoirs.

Evaluating the Transport Performance of Novel-Shaped Proppant in Slickwater Fracturing with the Multiscale Modeling Framework

Summary Recently, novel-shaped proppant, such as rod-shaped and x-shaped proppant, has been gradually used in hydraulic fracturing systems, which challenges the validity of previous transport laws for conventional spherical proppant. In this work, a multiscale modeling framework is proposed to solve this issue. We start from constructing particle-scale laws, including proppant settling, phase-slip, and effective slurry viscosity, based on a refined particle-resolved direct numerical simulation method, that is, the immersed boundary-computational fluid dynamics-discrete element method (IB-CFD-DEM). With this refined simulation method, particle-scale flow details are fully resolved, and accurate particle-scale laws can be reconstructed for novel-shaped proppant. These sub-scale laws are then applied to a field-scale simulation method, that is, the multiphase particle-in-cell (MP-PIC) method. Based on the proposed framework, transport performance of various types of proppant are investigated. Several numerical experiments demonstrate that proppant transport performance can be enhanced by 19 and 15% with x-shaped and rod-shaped proppant, respectively, compared to conventional spherical proppant under 5% inlet proppant concentration and enhanced by 16 and 10%, respectively, under 20% inlet proppant concentration. Moreover, related complicated flow mechanisms at different scales, such as the hindered effect and viscous gravity current effect, are fully discussed, which deepens our understanding of proppant transport and proppant placement.

Experimental study on fracture conductivity in high temperature and high pressure tight gas formation: A case of Tarim basin in China

With the increase in demand, deep and ultra-deep gas formations have been gradually explored and developed. As increasing the depth, the temperature and pressure were enhanced accordingly. Hydraulic fracturing is the main method to ensure a tight gas formation acquires high productivity. The fracture conductivity (FC) is a significant parameter to evaluate the flow capacity of fractures in a hydraulic fracturing design. FC was barely studied in the high temperature and high pressure tight gas formation. This study conducted the problem with Keshen formation in the Tarim basin in China. To evaluate FC in deep and high-temperature tight gas formations, we studied the impact of several crucial parameters, which are temperature, effective closure pressure, closure time, proppant type, proppant size, fracturing fluid, fracture roughness, and shear slip. Besides, we also considered the effect of pump proppant methods, static and dynamic pumping proppant on the fracture. Results showed that factors all had negative effects on the FC including higher temperature, higher effective closure pressure, smaller size proppant, lower proppant concentration, fracturing fluid addition, and increased closure time. Rough fracture surface and shear slip had a positive effect at the lower effective closure pressure. Moreover, we also found dynamic pumping proppant was more easily to form channel fracturing. The FC of the dynamic method was less than the static method when the effective closure pressure was larger than 50 MPa. This study provides a new approach to assess the FC in the high-temperature and high-pressure tight gas formation. Additionally, the mechanism of enhancing FC and production has been revealed through several key factors. This work facilitates engineers to optimize the hydraulic fracturing design and enhance the production of tight formations in the world.

Field experiments of different fracturing designs in tight conglomerate oil reservoirs

Mahu oilfield is currently the largest tight conglomerate reservoir in the world, where Ma-131 and Ma-18 plays are the first two commercially developed reservoirs. In order to reduce the cost and explore the best fracturing parameters, field experiments have been conducted in these two plays since 2017. Types of proppant and fracturing fluid, the slickwater ratio, and the fracture spacing are mainly changed for comparison, and fracturing effects are evaluated to establish a reference for developing neighboring plays in the Mahu oilfield. This paper summarizes the fracturing parameters and production histories of 74 wells in Ma-131 and Ma-18 plays during four years of field operations. Firstly, results indicate that silica sands perform similar to ceramics in the Ma-131 play where the reservoir depth is smaller than 3300 m; however, in the Ma-18 play where the reservoir is deeper than 3500 m, increasing the sand volume by 1.1–1.2 times still cannot reach the production in wells using ceramics. Secondly, when the fracture spacing is reduced, both oil production and water flowback become even smaller in wells using sands than those using ceramics; this is due to the increase of closure pressure and decrease of fluid volume per cluster respectively. Thirdly, when the crosslinked guar is replaced by the slickwater, no obvious change in oil production is noticed even though the volume of fracturing fluid is almost doubled; limited lengths of propped fractures due to the poor proppant-carrying ability of slickwater likely offset the production enhancement from the decrease of formation damage by slickwater. This paper summarizes learnings from the field experiments during the four-year development of the Mahu oilfield, and help guide the optimization of hydraulic fracturing parameters for future wells.

Effective Stress Factor Analysis of Proppant for Multi-stage Fracturing in Horizontal Wells

In order to determine the effective stress factor of proppants during the multi-stage hydraulic fracturing operation in horizontal wells and select the appropriate proppant type, the analysis of the effective stress characteristics of proppants is carried out. This analysis considers the geomechanics and long-term production characteristics of multi-stage fractured horizontal wells in reservoirs like Xinjiang Mahu shale oil and Southwest China shale gas. The analysis of influencing factors is also carried out. The results show that, during the multi-stage hydraulic fracturing operation in horizontal wells, the stress on proppants is not only related to geological factors such as reservoir closure stress, but also closely related to total injection volume, cluster spacing, liquid type, injection displacement and post fracture management. First, increasing injection intensity, reducing fracture spacing, using low viscosity fracturing fluid, adopting high injection displacement and utilizing reasonable flowback system can effectively supplement reservoir energy, postpone the effective stress peak of proppants, and increase the effective conductivity of proppants. Second, the production performance analysis results of nearly 300 horizontal wells (from Xinjiang oil field, Erdos tight oil reservoir, Sichuan shale gas reservoir, etc.) shows that: the effective stress of proppants in horizontal wells is only 50–60% of that in vertical wells, which results in a different proppant selection criterion in the volume stimulation of horizontal wells and provides the geomechanics basis of replacing ceramsite proppant with quartz sand to reduce cost and increase efficiency. Based on the above conclusions, the field test of replacing ceramsite proppant with quartz sand was carried out. The proportion of quartz sand increased from less than 30% in 2014 to 69% in 2019. Without any impact on production, the annual investment cost was decreased by more than 1 billion yuan, which set a great example for the promoted low-cost development of unconventional oil and gas reservoirs under low oil price background.

Improvement of Hydraulic Facing Technology by Modeling Permeability Formed Cracks for Specific Mining and Geologi-cal Conditions

The article describes the improvement of hydraulic fracturing technology by modeling the permeability of the formed fractures for specific mining and geological conditions. The description of the main indicators of the properties of the propping material for hydraulic fracturing is given. To prevent undesirable consequences when using various proppants in a number of Russian fields, testing was carried out for the proppant compliance with the ANI RP-56 standard, the results of which are shown in the article. Shown that it can be seen that the type of proppant and its physicochemical characteristics significantly affect the permeability of the hydraulic fracture. Therefore, only after conducting studies to assess the permeability in conditions close to reservoir conditions in the well, it is possible to select the type of proppant for hydraulic fracturing, potentially the most effective for specific mining and geological conditions. Concluded that the correct choice of proppant material for hydraulic fracturing minimizes the percentage of the probability of fracture of the proppant grains in the hydraulic fracture, as well as the removal of proppant grains into the wellbore, which ultimately has a positive effect on the well operation during development and operation in design mode.

Experimental Study on Fracturing Fracture Deformation Mechanism of Shale Reservoir

After large-scale sand fracturing of horizontal wells in shale gas reservoir, fracturing fractures will deform in the production process. However, fracture deformation will lead to the decrease in fracture conductivity and then cause the decrease of gas well productivity. Therefore, in order to evaluate the fracturing fracture deformation mechanism of shale reservoirs, the shale proppant-supported fracture deformation evaluation experiments were carried out under different proppant types, particle sizes, sanding concentrations, and closure pressure conditions, respectively, and the variation curves of fracture width was calculated by a stereomicroscope under different experimental conditions. Then based on the experimental results, the fracture sensitivity factors and fracture deformation mechanism were analyzed, and the deformation mechanisms of fracturing fractures affected by proppant embedding and crushing were studied emphatically. The analysis results of fracture sensitivity factors indicate that the larger the particle size and hardness of proppant, the lower the sand concentration, proppant embedded on the shale rock surface. Moreover, the deeper the proppant is embedded, the faster the fracture conductivity decreases. In addition, the greater the closure pressure, the more serious is the proppant embedment, and the faster the fracture width decreases. The analysis results of fracture deformation mechanism show that, on the on hand, under variable closure pressure, the proppant with larger hardness and larger particle size is used for fracturing, and the proppant embedded in the fracture surface is the main cause of fracture deformation. However, if only the sand concentration of the proppant in the fracture is changed, the fracture deformation is jointly dominated by the embedding and crushing of the proppant. On the other hand, under constant closure pressure, the main mechanism of fracture deformation is that the proppant is embedded into the fracture surface when the closure pressure is low, but if the closure pressure is high, the main mechanism of fracture deformation is the crushing and compaction of proppant.

A new proppant type fully coupled fiber-proppant and its property evaluation for unconventional reservoirs

Fracturing (hydraulic fracturing technology) treatment in an unconventional reservoir was a key technology. For an increased in production, effective proppant placement in hydraulic fracture systems was important in operating conditions. Especially, two key factors, proppant transportation distance and packing height, determined the final conductivity and gas production. This study aimed to develop a new type of proppant and evaluated its properties. Based on two new types of materials that could modify the surface of the proppant and fiber, the fiber and proppant coupled with each other due to the surface treatment and could transport longer and pile up higher in the fracture. Therefore, to furtherly figure out this new proppant property, visual fracture models were designed and used with some key factors. This study showed that this new proppant had some remarkable properties and had a better transportation efficiency in visual fracture models.

The Sound of One Fracture Flowing

In November 2020, Gustavo Ugueto had an extraordinary in-well experience. The source of his amazement was a stream of fiber-optic data measuring how fractures were altered by slight pressure changes during production. When the principal petrophysicist for unconventional technology at Shell described the Permian well test, he sounded like someone who had used a stethoscope for the first time. “The straining is extended and compressed at all times like breathing,” Ugueto said during a presentation at the 2021 Unconventional Resources Technology Conference (URTeC) about the test done at the Fracturing Test Site 2 in late 2020 (URTeC 5408). He said it was an “aha moment,” as was getting a good signal considering the infinitesimal differences in the fracture dimensions in a well where the daily pressure drop was less than 40 psi. And he was excited to think about what this test could reveal someday about how fractures change during production. If it lives up to that potential, “we will have the ability to measure. We can experiment. What type of treatment? What type of proppant? We can do more of the good one and less of the bad one. The problem [now] is we have been working blind,” he said. While he was clearly excited about the potential, he also repeatedly cautioned that there is so much more work required to learn what is possible. At this point, the few people with access to this data are like new medical students using a stethoscope, wondering how those sounds related to the patient’s health. “We are at the beginning of journey; it may fail,” Ugueto said. The New Strain The data from the Hydraulic Fracture Test Site 2 are only available now to those who backed the project, but three papers cover the work (see For Further Reading), sparking others to try this new way to measure fractures. “Because of the publications by Gustavo and his coauthors, we are seeing a lot of uptake based on what was learned,” said Dana Jurick, Neubrex Energy Services US—the company that supplied the equipment used to measure the strain data. The company has since been hired for similar work by other oil companies curious about what they can learn from this new diagnostic. The coauthors include Ge Jin, an associate professor at the Colorado School of Mines, who was a geophysics consultant at the Hydraulic Fracturing Test Site 2, and Kan Wu, an associate professor at Texas A&M, who is collaborating with Jin. Her group at Texas A&M is working on modeling aimed at turning this qualitative data source into a quantitative measurement. Ugueto said other operators trying it, including Chevron and ConocoPhillips who were among the test site partners, plus other fiber-optic companies, are getting into a field that is so new there is no settled name for it. Two commonly used labels for it reflect varying levels of optimism about its future. One is based on the data gathered: near-wellbore strain analysis. The other is based on a vision where it is possible to measure how fractures react to change: near-wellbore fracture dynamics.

Controlling factors of fracture aperture reduction based on experimental study using proppant pack apparent Young's modulus

The hydraulic fracture aperture packed by proppants determines the fracture conductivity and is pivotal to oil and gas production. After hydraulic fracturing, the fracture width decreases owing to proppant embedment, deformation, and crushing. However, the analysis of fracture width reduction based on the mechanical properties of the proppant pack is limited. In this study, an experiment is designed to obtain the apparent Young's modulus, which represents the rigidity of the entire pack, and steel sheets are used to replace rock samples to eliminate heterogeneity and weaken the effect of proppant embedment. Subsequently, the effects of proppant type, concentration, and size on the apparent Young's modulus are discussed. Finally, the controlling factors and mechanisms of fracture width reduction are determined. The results indicate that the fracture width decreases linearly with increasing closure pressure for the ceramsite pack, and that the apparent Young's modulus is associated with the fracture aperture variation, which is governed by proppant embedment and deformation. The apparent Young's modulus increases as the proppant concentration increases or the proppant size decreases, whereas the proppant size imposes a more prominent effect. However, the mixed-size ceramsite pack shows only slight improvements in terms of propping ability. This study provides new insights into factors governing proppant pack deformation. • The apparent Young's modulus is defined through experimental results to quantitatively characterize mechanical properties of the whole proppant pack. • The proppant pack will experience at least 1 rigid-to-plastic deformation cycle under closure pressure. • The apparent Young's modulus for ceramiste can be inserted into fracture width calculation correlation, of which the fracture width decrease is mainly dominant by proppant embedment and deformation. • Proppant concentration and size both have influence on apparent Young's modulus, but the latter is more profound . The finer the particles are, the higher the modulus of the proppant pack is.

Facile and Controllable Preparation of Poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants.

Hydraulic fracturing is an important technology for the exploitation of unconventional oil or gas reservoirs. In order to increase the production of oil or gas, ultra-lightweight proppants with a high compressive strength are highly desirable in hydraulic fracture systems. In this work, a new type of ultra-lightweight proppant, poly(styrene-co-methyl methacrylate)/fly ash (poly(St-co-MMA)/FA) composites with a high compressive strength were prepared via in situ suspension polymerization. The Fourier transform infrared (IR) and X-ray powder diffraction (XRD) analyses confirmed that the poly(St-co-MMA)/FA composites were successfully prepared. The morphology analysis indicated that the composite microspheres show good sphericity, and FA powder was evenly dispersed in the matrix. The apparent density of the microspheres was between 1 and 1.3 g/cm3, which is suitable for hydraulic fracturing. Furthermore, the compressive strength and thermostability were dramatically improved with the incorporation of FA, which could withstand high pressures and temperatures underground. The obtained poly(St-co-MMA)/FA composite microspheres are promising for application as an ultra-lightweight (ULW) proppant in oil or gas exploitation, which provides a new approach for the design of high performance proppants.

Experimental simulation of proppant permeability in hydraulic fracturing at extended time under bottom-hole conditions

During hydraulic fracturing treatment, huge quantities of gel are pumped into the formation to initiate the fracture, maintain it open and transport the proppant. The fracture dimensionless conductivity (Fcd) is a key parameter to optimize the fracturing design, to estimate the productivity Index (PI) and the folds of increase (FOI). However, these parameters are affected by the gel residues which decrease the fracture conductivity; thus, the proppant cleanup is a very important step to avoid additional damage caused by fracturing fluid due to high gel concentration and the extended time of gel staying in the fracture before cleanup. Throughout the life of Hassi Messaoud, Algeria field, hydraulic fracturing technique has been aggressively used mainly in four producing formations in the Cambrian, with hard formation characteristics, an average permeability range and low reservoir pressure (0.15–0.45 psi/ft) and high stress value between 6000 and 9000 psi. In this paper, an experimental simulation is applied using a self-made cell to determine the effect of different parameters on the fracture conductivity under various bottom-hole conditions where different variables were used: effect of Proppant type, guar gel concentration, temperature, breaker concentration and closure pressure at extended time. An important drop in fracture conductivity was observed varied between 10 and 80% under stresses at interval of 2000 psi and 8000 psi, gel concentration up to 200 lb/1000 gal at extended time and temperature.

Pressure-dependent flow characteristics of proppant pack systems during well shut-in and the impact of fines invasion

Near-wellbore screenouts during the shut-in stage due to the development of compact proppant clusters is an issue reported in several fracturing treatments for Coal Seam Gas (CSG) reservoirs. The usual solutions to counter this issue implemented in deep rocks such as Shale and Siltstone do not solve for coal reservoirs due to its geological characteristics. Therefore, the development of proppant packs is an expected outcome during CSG extraction, and the permeability in the proppant pack could decide the overall gas productivity. This study investigates the permeability of proppant packs prepared using the Under-compaction method to simulate compact proppant clusters experienced in near-wellbore screenouts. In this regard, two commonly used proppant types are selected; sand and ceramic, and a series of tri-axial permeability tests were conducted under various effective stresses relevant to CSG environments. According to the experimental outcomes, interestingly, both proppant packs exhibited non-Darcy and Darcy flow regimes, while the non-Darcy effect was more profound at low confining pressures due to its high packing porosity. Results showed that the permeability through the compact proppant pack depends on both the reservoir pressure and the type of proppants selected. The sand proppant pack (SPP) showed 1–2 orders higher than the permeability values of the ceramic proppant pack (CPP) until a threshold pressure is reached (10 MPa), after which the ceramic proppants produced higher permeability values. We also investigate the potential impact of the invasion of coal fines into the proppant packs and the corresponding pore blockings. The impact of fines invasion on CPP permeability was more potent compared to the fines induced SPP permeability. The shape of the ceramic particles, the polar effect of the α-Al2O3 atoms, and the attraction of the oxygen functional groups of the coal fines to these polar sites increase the likelihood of fines clogging in a ceramic proppant pack.

Experimental investigation of long-term fracture conductivity filled with quartz sand: Mixing proppants and closing pressure

With the rapid technological advances in hydraulic fracturing, the economic development of ultra-tight gas/oil reservoirs becomes feasible, altering current energy image between demand and supply. The key parameter evaluating the artificial hydraulic fracture is the long-term conductivity, manifesting the transport capacity for reservoir fluids. The majority of previous contributions focused on the impacts of inherent proppant properties on long-term fracture conductivity, while the influence induced by mixture proppants with a wide range of particle size has not received due attention. In particular, as for the realistic field case, multiple types of proppants with diverse particle sizes are utilized to reach desirable conductivity. At the same time, the stress conditions inevitably change within the depressurization development process, leading to the evident enhancement of closing pressure towards artificial fracture, acting as the detrimental role for long-term fracture conductivity. As a result, it is dramatically necessary and urgent to reveal the mutual influence arising from mixture proppants as well as closing pressure. In order to address this issue, series of laboratory experiments are implemented, and comprehensive theoretical analysis in terms of experimental data is performed. Results show that (a) reduction of particle size is observed with increasing closing pressure, the average decreasing rate approaches 19.3%; (b) Closing pressure acts as a detrimental role impairing conductivity, the amplitude is able to reach 42.1% as for the mixture case with a relatively high proportion of mesh-20/40 particles; (c) Mixing proppants uniformly fails to enhance fracture conductivity effectively, and the forward segmentation is demonstrated as the suitable strategy and beneficial for fluid transport capacity. The contribution expects to advance current understanding regarding the impact of mixture proppants on long-term fracture conductivity.

Effective application of proppants during the hydraulic fracturing of coal seam gas reservoirs: Implications from laboratory testings of propped and unpropped coal fractures

Commercial production of coal seam gas is a significant proportion of the total Worldwide natural gas supply due to its high gas storage capacity at shallow extraction depths. Coal seam gas recovery may be enhanced by pure fluid-based or proppant based hydraulic fracturing – the decision whether or not to use proppants depends on coal seam characteristics – in particular stress-permeability characteristics. Although proppant application has been common in deep reservoir fracturing, its application on soft rocks such as coal should be carefully investigated. Higher concentrations of proppant are known to minimise proppant damage in deep reservoirs, with stiffness and flow tortuosity also impacting the response. We explored the impact of proppant loading, coal type and fracture roughness on fluid flow characteristics in propped fractures by conducting a series of triaxial permeability experiments combined with micro-CT imaging. The results reveal that proppant application in coal is only effective for deep coal seam gas reservoirs with effective stress greater than 6 to 8 MPa (~700 to ~900 m). Further, proppant application may cause up to 1–2 folds of fracture conductivity improvement in coal seam gas reservoirs located at over 1.2–1.4 km depths (effective stresses > 12 MPa). The impact caused by proppant embedment on fracture conductivity degradation is much significant compared to other proppant damage mechanisms. The effect, however, depends on the stiffness of the coal rock matrix and the proppant type implemented.

Research on the Synthesis of Proppants Applied for Oil Production by the Method of Hydraulic Facing

The essence of the hydraulic fracturing method for enhancing oil recovery is described. The definition of proppants is given and their average chemical composition is determined. In the process of an analytical review, the article presents proppants that are widely used in the oil industry. For each type of proppant, the main technical characteristics (bulk density and compressive strength) required when using the hydraulic fracturing method have been determined. In the course of the analysis, it was found that all proppant technologies are expensive and it is necessary to select high-quality cheap and affordable materials to reduce the cost of their production. Drilling cuttings from the Morozovskoye field were chosen as one of these materials. Physical and chemical studies of drill cuttings were carried out, on the basis of which a conclusion was made about the possibility of its use in the synthesis of high-quality aluminosilicate proppants.

Evaluation of main factors affecting fractured horizontal well productivity of tight sand gas reservoir in Sichuan Basin

Hydraulic fracturing horizontal well is the key technology of tight gas development. After fracturing, the gas well shows the characteristics of great difference in production energy and many factors affecting production capacity. Therefore, taking 10 fractured horizontal wells in JQ gas field in Sichuan Basin as an example, comprehensively considering the influence of geological and engineering factors, and based on the statistical analysis of gas well productivity and the laws of various index parameters, 17 geological and engineering parameters were selected, and the main factors controlling productivity were studied by grey correlation method. The results show that the tight gas fracturing horizontal well can obtain high production, which is jointly determined by geological and engineering factors. The five main control factors affecting the productivity of tight gas fracturing horizontal well are as follows: proppant type, preflush, ϕ·h. Sand volume and reservoir volume.

Characterization of Baram and Tanjung sands as potential proppants

Baram and Tanjung sands were evaluated for potential use as proppants. Experiment was conducted on Baram and Tanjung sands following ISO and ASTM recommended standards. Results showed that Baram and Tanjung sand mineralogy is predominantly quartz with presence of metal oxides. Shape descriptors of both sands for sphericity and roundness were above 0.7. Baram sand was retained by 20/40 mesh size with mean size of 448.2 μm, bulk density of 1.32 g/cc, acid solubility of 1.5% and crush resistance of 4000 psi. While Tanjung sand was retained by 30/50 mesh size with mean size of 383.2 μm, bulk density of 1.30 g/cc, acid solubility of 1.20% and crush resistance of 8000 psi. This indicates that Baram sand has larger grain size that supports high permeability at low closure stress, making this sand suitable for shallow depth hydraulic fracturing operations, whereas Tanjung sand is more suitable for deeper domains with high closure stress. Experimental results and economic comparison with commercial frac sand and other proppant types support using Baram and Tanjung sands as potential proppants.