Resin-coated Sand Research Articles

Appraisal of the Propping Potential of Luwa Sand in Nigeria for Hydraulic Fracturing Applications

Natural sands made of spherical and round grains are widely used as proppants during hydraulic fracturing to increase recovery rate of hydrocarbon production. Synthetic proppants with high crush strength are employed for deep reservoir fracturing; however, this type of proppants suffer the disadvantages of high density, high cost and pose environmental hazards. This research was conducted with the aim to assess sands collected from Luwa River in Toro, Bauchi state of Nigeria for possible use as natural sand proppants. An epoxy resin-coated sand was produced using a simple method to modify the sands’ properties. A series of experiments were conducted in accordance with API recommended practice to determine the propping potential of the sand and the resin coated sand. The result from sieve analysis of 20/40 mesh size of Luwa sand revealed a mean size of 625.2 microns (0.625 mm). An X-ray fluorescence (XRF) result showed the presence of aluminosilicates (Al2O3 and SiO2) composition in Luwa sands. The sands recorded a hardness of 8 on the Mohs scale. Analysis of the shape parameters for sphericity and roundness was 0.8 and 0.8 (Krumbein-Sloss) respectively; it has bulk density of 1.64 g/cm3, acid solubility of 0.7% and 4.32% for the resin-coated sand. The sand has turbidity value of 28.98 NTU, loss on ignition in the range of 1.33% to 1.64% and crush resistance varies between 2000-3000 psi for Luwa sand and 4000-5000 psi for the coated sand. A comparison of the experimental results with API standard and conventional Ottawa and Brady models showed the sand competes favourably with these standards in all parameters for consideration as a proppant except for the crush resistance where more than 10% fragments was generated at low pressure of 3000 psi. However, the sand can be applied in shallow depth reservoirs.

Appraisal of the Propping Potential of Luwa Sand in Nigeria for Hydraulic Fracturing Applications

Natural sands made of spherical and round grains are widely used as proppants during hydraulic fracturing to increase recovery rate of hydrocarbon production. Synthetic proppants with high crush strength are employed for deep reservoir fracturing; however, this type of proppants suffer the disadvantages of high density, high cost and pose environmental hazards. This research was conducted with the aim to assess sands collected from Luwa River in Toro, Bauchi state of Nigeria for possible use as natural sand proppants. An epoxy resin-coated sand was produced using a simple method to modify the sands’ properties. A series of experiments were conducted in accordance with API recommended practice to determine the propping potential of the sand and the resin coated sand. The result from sieve analysis of 20/40 mesh size of Luwa sand revealed a mean size of 625.2 microns (0.625 mm). An X-ray fluorescence (XRF) result showed the presence of aluminosilicates (Al2O3 and SiO2) composition in Luwa sands. The sands recorded a hardness of 8 on the Mohs scale. Analysis of the shape parameters for sphericity and roundness was 0.8 and 0.8 (Krumbein-Sloss) respectively; it has bulk density of 1.64 g/cm3, acid solubility of 0.7% and 4.32% for the resin-coated sand. The sand has turbidity value of 28.98 NTU, loss on ignition in the range of 1.33% to 1.64% and crush resistance varies between 2000-3000 psi for Luwa sand and 4000-5000 psi for the coated sand. A comparison of the experimental results with API standard and conventional Ottawa and Brady models showed the sand competes favourably with these standards in all parameters for consideration as a proppant except for the crush resistance where more than 10% fragments was generated at low pressure of 3000 psi. However, the sand can be applied in shallow depth reservoirs.

Novel Resin-Coated Sand Placement Design Guidelines for Controlling Proppant Flowback Post-Slickwater Hydraulic Fracturing Treatments

Summary Resin-coated sand (RCS) is an effective way for controlling post-stimulation proppant flowback. However, with the shift to slickwater treatment fluids, the “tail-in” placement approach has proved to be less efficient for complete flowback control due to the proppant settling characteristics of using low-viscosity fluids. A new RCS placement approach was developed based on the results of several flowback studies. Trial wells were completed in different US basins with successful results. Proppant flowback samples were collected during different stages of drillout and production from wells using slickwater fluid systems. Thirty-five wells, completed by thirteen different operators, within the Permian and MidCon basins were evaluated. All wells were completed using multiple proppant mesh sizes. A total of 375 flowback samples were collected during the drillout and production phases. The samples were sieved, and the results were fed into an in-house material balance model to determine the percentages of different mesh sizes in the flowback samples. The conclusions were used as guidelines for a new placement approach implemented in multiple new wells to control proppant flowback. The flowback samples ranged from predominantly lead proppant to a similar proportion of the pumped mesh sizes. Not one of the 35 wells had flowback samples containing the majority tail-in mesh size. This supports the early sand dune assumption, suggesting that the early proppant forms dunes near the wellbore and late sand settles over the existing proppant beds. The use of late RCS appears to have a minimal effect on preventing flowback of the early proppant within a stage utilizing slickwater fracturing. Therefore, RCS efficiency to control proppant flowback with the tail-in method is reduced when used in such slickwater stimulations. To seal the different proppant beds, the new approach recommends pumping multiple RCS steps within a stage. The first RCS step is recommended within the first 10–20%, the second sequence within the first 40–60% of proppant volume, and the third as a tail-in. The exact percentages and step design were based on the results of flowback samples from neighboring wells. The implementation of this approach in more than 30 wells resulted in superior flowback control compared to offset control wells. In all trials, the proppant flowback completely stopped within 1 to 7 days of starting production. In this paper, we discuss the drawbacks of the current RCS placement practice while suggesting a new practical approach supported by data. RCS tail-in showed successful flowback control with viscous fracturing fluids and hybrid systems. For slickwater systems, an optimized placement design for RCS throughout the pump schedule provided enhanced flowback control compared to RCS tail-in. Finally, we illustrate the results of field trials in which utilizing the new RCS placement approach successfully reduced flowback.

Feasibility of Proppant Flowback Control by Use of Resin-coated Proppant

Proppant flowback is a problem in Xinjiang oilfield. It decreases production rate of a fractured oil well, corrodes surface and downhole facilities and increases production costs. Curable resin-coated sand is a common technique to control proppant flowback. This article presents an experimental investigation whether it is feasible to control proppant flowback by use of resin-coated sand and whether resin-coated sand has a negative effect on proppant pack conductivity. It included two kinds of experiments, Proppant flowback experiment measured critical flow rate while the Proppant pack conductivity one measured proppant conductivity. The experimental results of proppant flowback show that the critical flow rate of resin-coated sand is far greater than that of common sand which means proppant flowback would not happen by resin-coated sand tail-in. Compared to Xinjiang sand conductivity, resin-coated sand conductivity is far smaller though it declines slightly which means use of resin-coated sand would lead to conductivity loss and sequentially results in production impairment. Experimental results show that it is feasible to control proppant flowback by use of resin-coated sand and resin-coated sand would affect fracture conductivity of a fractured oil well. Based on the experimental results, resin-coated proppant conductivity can be improved by use of resin-coated ceramic or liquid-resin-coated proppant. The achievements can give a direction towards how to select a resin-coated proppant and how to improve resin-coated proppant.

A Study on a New Type of High-Performance Resin-Coated Sand for Petroleum Fracturing Proppants

This study investigates a new type of high-performance coated sand as a petroleum fracturing proppant material. Modified quartz sand was coated with a layer of low-density resin to reduce the overall density of the proppant, thereby improving the suspension of the proppant in the fracturing fluid. Resins play an important role in the preparation of coated sand fracturing proppants. The mechanism of sand formation was studied by examining the phase composition and microstructure of the coated sand proppant. The results demonstrate that when the polyimide resin content is 6% and the curing temperature is 180 °C, the proppant exhibited the best performance with an apparent density of 1.592 g/cm3 and a breakage ratio of only 3.22% under 55.2 MPa. Compared with the widely used epoxy resin-coated support agent and phenolic resin-coated support agent in the early stage, their crushing rate decreased by 5% and their acid solubility decreased by 2%. Hence, this study is worthy of attention.

Influence of Differences between Resin-Coated Sand and Green Sand and Defferences in Compactablity of Green Sand on Blow Molding Behavior

Influence of Differences between Resin-Coated Sand and Green Sand and Defferences in Compactablity of Green Sand on Blow Molding Behavior

Effect of Silica Content on the Surface Quality of Cast Iron in Shell Mould Process

Resin Coated Sand (RCS) is an important raw material for the Shell mould process. This research aimed to study the effect of silica content on the surface quality of cast iron in the shell mould process. The four kinds of sand are Australian sand, Rayong sand, Reclaimed sand and River sand. All sand was mixed with phenolic resin for making Resin Coated Sand. The chemical composition of sand was tested by X-Ray Fluorescence. The result found that the SiO2 content of each sand was different. The SiO2 content of Australian sand 99.8%, Rayong sand 98.6%, Reclaimed sand 90.3% and River sand 89.2%. The morphology from the microscope was found that sand grains exhibited different shapes that affect mechanical properties such as bending strength and thermal expansion of Resin Coated Sand. The qualification of Resin Coated Sand is bending strength and thermal expansion from Australian sand is the highest. On the other hand, River sand is the lowest bending strength and thermal expansion. The casting result showed that the burn on and veining defects were found on the casting surface. The veining occurred with Australian sand. While, the burn on occurred with Rayong sand, Reclaimed sand and River sand.

Source Analysis and Countermeasure Research of Sand Production after Hydraulic Fracturing in Tight Sandstone Gas Reservoir

Abstract Sand production is the most common problem after hydraulic fracturing treatment. This problem is particular prominent in sandstone reservoirs. For Jinqiu gas reservoir of Sichuan Basin in China, the average sand production after fracturing is 103 tons, and the sand production rate is 2.36% through statistics of 12 wells. The sand production will seriously damage the downhole equipment as well as ground facilities. In this study, based on the analysis of sand production source, it is clear that the sand production mainly is 70/140 mesh sand flowback after hydraulic fracturing treatment. In order to control this proppant flowback, average fibers length of about 3 mm, 6 mm, 9 mm, and 12 mm are selected for proppant flowback control experimental study. A series of laboratory evaluations are designed to quantify the effectiveness of fibers on proppant flowback control, so as to explore the mechanisms behind for optimizing their properties for a chosen reservoir. The key fiber properties include dispersion performance, microstructure, the influence on proppant transport in fracture, fracture conductivity, and critical flowrate. The dispersion of fibers with different lengths and concentrations in slickwater is good, and the fibers can form a net-like structure that reinforces the pack, and for 70/140 mesh sand and 40/70 mesh resin-coated sand, with the increase of fiber length and concentration, the sand transport distance and critical flowrate increase, but fracture conductivity decreases. The field test is carried out through the fiber type and dosage optimized by indoor experiment. A systematic indoor evaluation and field test shows that fiber plays a significant role in proppant flowback control. The findings of this study can help for a better understanding of the source analysis and countermeasure research of sand production after hydraulic fracturing in tight sandstone gas reservoir.

High strength glass beads coated with CNT/rGO incorporated urethane coating for improved crush resistance for effective hydraulic fracturing

Hydraulic fracturing is a widely employed well stimulation technique in which a synthesized fracking fluid is pumped into the well bore at high pressures to propagate fractures in rock formation matrix for hydrocarbon production. Proppant being one of the essential component of fracturing fluid is used to keep the hydraulically induced fractures open and conductive by acting as a mechanically strong support particle. Hydraulic fracturing operations are gradually shifting into deeper and low permeability (tight) formation at elevated temperature and pressure conditions at which conventionally used silica sand is becoming unviable as proppant due to its crushing. For resin-coated sand (RCS), temperatures greater than 60°C under high pressures, the glass transition temperature (Tg) threshold limit of polyurethane-based resin coating is reached at which this applied coating tends to soften that results reduction in the mechanical strength of the coated sand pack. Glass beads are also considered as good contestant for proppant that were selected in this study due to their high roundness and sphericity. They were drip coated with urethane resin incorporated with three different concentrations of 0.1 wt%, 0.5 wt% and 1 wt% carbon nanotubes (CNTs) and reduced graphene oxide (rGO) nanofillers, respectively. Crush test analysis by means of Universal Testing Machine (UTM) revealed significant improvement in the mechanical strength of coated glass bead proppants. 0.5 wt% loading of CNTs into urethane resin proved to be the best optimum concentration at which the mechanical strength of the coated glass bead improved by 84% along with 40% reduction in fines generation due to its containment within the applied coating. Crush test results also further revealed that nanofillers concentration loadings greater than the optimum threshold limit into urethane resin promoted their mutual agglomeration that resulted in profound reduction in mechanical strength of coated glass beads therefore resulting in more crushing and higher generation of undesired and detrimental fine particles.

Proppant Diagenesis in Carbonate-Rich Eagle Ford Shale Fractures

SummaryProppant diagenesis occurs when minerals form on the proppant surface and/or around the embedment crater at high-temperature and/or high-stress conditions (Weaver et al. 2005). It has been used recently to explain low fracture conductivity in the field as well as the long-term downward trend of laboratory-measured American Petroleum Institute conductivity data (Liang et al. 2015). However, researchers disagree about the source of such overgrowth minerals and the involvement of proppant in the process. In addition, the diagenesis process has not been investigated in the case of carbonate-rich shale formations. Therefore, the objectives of this paper are to experimentally investigate the proppant diagenesis process during hydraulic fracturing of the Eagle Ford Shale Formation and to determine the role of the proppant in the process.Diagenesis was studied after aging a mixture of proppant and formation samples in deionized water for 3 weeks at 325°F and 300 psia. Outcrop cores of the Eagle Ford Shale Formation were crushed and sieved to 50/100 US-mesh size. The ceramic, sand, and resin-coated-sand (RCS) proppants of 20/40 US-mesh size were tested. The proppant surface was studied for mineral overgrowth and/or dissolution before and after aging using scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS). The concentration of the cations leached into the solution was measured by analyzing the supernatant samples using inductively coupled plasma (ICP)/optical-emission spectroscopy, while the sulfate-ion concentration was measured using a spectrophotometer. The proppants and the Eagle Ford Shale Formation samples were analyzed after aging separately at the same conditions to explain the sources of the leached ions and the observed overgrowth and/or precipitated minerals.The Eagle Ford Shale was found to be the source of calcium sulfate and calcium zeolite precipitates because of dissolution/precipitation reactions with water. Only the ceramic proppant was found to induce an additional mineral overgrowth of iron calcium zeolite on its surface. Conversely, the sand and RCS proppants did not encounter any precipitates/overgrowth minerals. These proppants only changed the elemental composition of the precipitated zeolite from the formation/fluid interaction, showing increased silicon and decreased calcium and aluminum concentrations. The proppant dissolution was observed with all types of proppants, as indicated by the presence of silicon ions in the solution after aging. A thermodynamic modeling study was conducted and confirmed the possibility of formation of the observed precipitate and overgrowth minerals at the equilibrium state of the rock and proppant mixture in water. Finally, the breaking and peeling of the phenol formaldehyde resin from the RCS proppant particles at static conditions was observed for the first time (to the best of the authors’ knowledge) using the SEM technique.The study contributes to the understanding of the scale formation and the mechanisms that damage fracture conductivity in the Eagle Ford Shale. Results impact the choice of fluid and proppant for fracturing optimization and long-term production sustainability in the Eagle Ford Shale reservoirs.

Pengaruh Waktu dan Temperatur terhadap Sifat Mekanik Pasir dan Kualitas Produk Cor dengan Metode Shell Moulding

The shell molding method is one of the processes of coating sand grains in a thermo setting resin which preserves heat on the model. To produce castings products that have good quality and produce maximum mechanical properties from the shell molding process, it must be known that the right procedure stages such as the right heating time. But currently there is no technical procedure that is found that is the right temperature and heating time for making shell molding to produce good surface quality of castings. This study aims to determine the effect of temperatures and heating time on the mechanical properties of RCS (resin coated sand) and the quality of the object castings. A series of testing methods, carried out by heating the RCS on the sample mold bending and hardness test. Testing the mechanical properties of sand includes bending test and hardness test. The time variations used in sand heating are 1 minute, 2 minutes and 3 minutes with temperature variations of 1800C, 2000C, 2200C, 2400C, 2600C and 2800C. After knowing the results of the most optimal temperature and time from testing mechanical properties then making molds using the shell molding method, the molding material used is aluminum. The mold formed from the shell molding method is then cast using NiHard1 material with a temperature of 14000C. The results of the castings will be identified visually and compared with the mechanical properties of the sand obtained. The results of this study obtained the highest value on the graph of the results of mechanical properties testing at a temperature of 2200C with a heating time of 2 minutes. The results of castings best viewed in terms of visual obtained by heating time for 2 minutes and 3 minutes at a temperature of 2200C. This showed that the heating time for 2 minutes and 3 minutes at the temperature of 2200C results in the highest mechanical properties and the best quality of castings for shell molding method.

A new method to measure propped fracture width and proppant porosity in shale fractures

Hydraulic fracturing is the main stimulation method used to economically produce from shale formations. The method requires the injection of a fracturing fluid at a pressure, which is high enough to fracture the formation, and as a result, improves the well productivity. A proppant is pumped with the fracturing fluid to prevent the closure of the induced fractures after the treatment. The proppant inside the fracture is subjected to a high earth closure stress, which causes proppant crushing, embedment, and compaction mechanisms. The subsequent reduction of the fracture width and proppant porosity reduces the fracture conductivity and could be crucial to the success of the fracturing treatments. The available methods to evaluate such reduction do not take into account downhole stress or the compression of rock under stress. The objective of this study is to experimentally evaluate the reduction of the propped fracture width and proppant porosity between two shale samples using a new method that allows the direct viewing of the fracture at downhole conditions.A new experimental model was designed to measure fracture width and porosity of proppant under downhole conditions. Outcrop shale samples were used. Varies proppant types and sizes were used including: sand, resin-coated sand, and ceramic proppants of the sizes 20/40, 40/70, and 100-mesh. The proppants were tested at concentrations of 0.2, 0.4, and 0.6 lb/ft2. A high-pressure core holder with modified fittings was used to subject the fracture model to different closure stresses up to 8000 psia. A new method was used to evaluate the change in the propped fracture width and proppant porosity as a function of closure stress. The fracture width was measured by viewing fracture under stress using a digital borescope. The change in the proppant porosity was calculated at each stress and a sieve analysis was conducted to quantify the crushed proppant because of the applied stress.A set of tables were provided for the values of fracture width and proppant porosity under stress for each proppant type, size, and concentration. The proppant porosity under stress was found to be directly proportional to the proppant concentration and inversely proportional to the proppant size. The reduction in fracture width and proppant porosity due to stress ranged from 5.68 to 25.88%, and from 7.88 to 44.16%, respectively. The crushing of sand proppant was found to be as high as 28.03% at 8000 psia and 0.2 lb/ft2 proppant concentration, and reduced by increasing its concentration or decreasing its size. The embedment of ceramic proppant at 8000 psia reduced the fracture width by 29.2 and 32.5% for the Eagle Ford and Marcellus shale, respectively.The propped fracture width and porosity under stress can be used as inputs to well production models, reservoir simulation models, and fracture design calculations. The results can also be used in the proppant selection process to improve the fracture conductivity and maximize the well productivity of shale formations.

The Effect of Coefficient of Restitution in Modeling of Sand Granular Flow for Core Making: Part II Laboratory and Industrial Test

In this second part of the two-part article, a laboratory-scale core box, which is originally designed and built with a center wedge and slotted base, is adopted to validate the correlation tested in Part I between coefficient of restitution (COR) and flow performance of granular sand materials on a laboratory core shooter. A series of experiment is conducted as parametric study on the collision effect and fluid behavior by blown granular material of sand and resin mixture under air pressure with variation in binder and additive levels. Corresponding simulations are examined using numerical method of two-fluid modeling or two-phase flow. The result of sand distribution in the slots of the core box base after collision on the wedge is measured and analyzed through the “collision ratio.” The factorial analysis indicates a negative relationship between collision ratio and binder level, while the content of powder additive is highly possible to promote the flow-ability of binder-coated wet sand. The regression analysis also shows that a relationship between collision ratio and COR follows an exponential law. Similarly, the comparison of typical cores from simulation and experiment demonstrates a negative effect on the travel distance of the sand granule when COR decreases. Therefore, the final packing of the sand in the cavity decreases when sand flow-ability is reduced. Practically, for resin-mixed wet sand, it is more difficult to fill the core cavity to achieve full compaction over thin section and sharp corner in the cavity of the core box compared to that of dry resin-coated sand.

A novel method of indirect rapid prototyping to fabricate the ordered porous aluminum with controllable dimension variation and their properties

An indirect rapid prototyping method to fabricate ordered porous aluminum was carried out by combining the selective laser sintering and the infiltration casting. The preforms were designed by Pro/Engineer and fabricated by the selective laser sintering with the resin-coated sand. The aim of structure design and control for ordered porous aluminum was achieved. Meanwhile, the structure and mechanical property characterization of the ordered porous aluminum were studied. The results indicated that the specimens had higher porosity than the original models. The deviation appeared and accumulated mainly ascribing to the dimension variation between the sand preform and the preform model. The identical tendency of geometry variations could be utilized to revise the original model in order to compensate the dimension variation. The compressive stress-strain curves of the ordered porous aluminum for pure specimens showed the typical feature of porous materials and increased smoothly and continuously while ZL111 specimens had some peaks and drastically varied plateau regions. The infiltration temperature had an obvious effect on the compressive property for ZL111 specimens compared with pure aluminum specimens. The optimized structure and strengthened matrix made the ZL111 specimen had highest compressive strength 86.48 MPa and excellent energy absorption capacity in this study.

Evaluating a Ceramic Resin-Coated Sand for Aluminum and Iron Castings

Shell molding technology remains an important part of metal casting technology because it permits precision sand castings. However, there is a lack of information available on shell resin-coated sand (RCS) produced with ceramics. This paper relates the physical, mechanical, and thermo-mechanical properties of disc-shaped shell core specimens made from either silica or ceramic sands. Gravity-filled disc-shaped shell core specimens were fabricated with silica and ceramic sands. Specimens were laboratory tested and evaluated in aluminum and iron casting trials. Testing included density, abrasion, thermal distortion, hot permeability, impact and retained strength. All tests were accomplished according to newly adopted American Foundry Society standards. With a ceramic RCS, it is possible to produce cores and molds having superior abrasion resistance, strength, and thermal stability when compared to a silica RCS. Ceramic RCS shell core specimens showed fewer casting surface issues when compared to silica RCS shell core specimens in aluminum and iron casting trials.

Proppant-packed fractures in shale gas reservoirs: An in-situ investigation of deformation, wettability, and multiphase flow effects

The results of a systematic, micro-scale experimental investigation on two-phase gas/brine flow through proppant-packed fractured shale samples under increasing effective stresses of up to 5000 psi are presented in this paper. We use a miniature core-flooding apparatus integrated with a high-resolution X-ray micro-CT scanner to perform the flow experiments. Geomechanical deformation and its impact on displacement mechanisms governing fluid transport within the packed fractures are studied at the pore scale under certain flow and stress conditions. These conditions were carefully designed to represent reservoir depletion and transport of water through such media. Since proppant grains are placed to maintain the long-term conductivity of the induced fractures, they significantly influence the geomechanical and multi-phase flow behavior of these conduits during reservoir depletion. We particularly examined the effectiveness of modified resin-coated sand (compared to a basic white sand) in maintaining the hydraulic conductivity of induced fractures. Significant bullet-like embedment and proppant crushing under severe stress conditions were found to be the shortcomings of these proppants, respectively. We then developed a methodical framework to design improved proppants with a similar mechanical strength to the host shale rock to withstand these drawbacks.Sphericity, roundness, and size of the proppant grains also impacted the critical properties of the constructed pore space such as pore size distribution and pore-throat aspect ratio. Such parameters control pore-scale gas-to-brine and brine-to-gas displacements within the hydraulic fractures. We specifically studied the non-wetting phase trapping and its subsequent impact on reduction of available pore space for other fluids to flow. It was found that trapped gas globules are very likely to deform within the medium and redistribute/reconnect under a higher effective stress. For the first time, wettability alteration of the proppant pack from water-wet to oil-wet was observed in a gas/brine fluid system. Wettability alteration occurred non-uniformly and was thought to be due to deposition of the shale organic matter released after significant proppant embedment. Such wetting characteristics aggravate multi-phase trapping within the fractures, which in turn leads to dramatic reductions in effective gas permeability. This study is concluded with a set of recommendations that can be used to effectively maintain the productivity of propped fractures for extended period of time.

Crushing characteristics of four different proppants and implications for fracture conductivity

Proppants are widely used during hydraulic fracturing in the oil and gas industry. This paper compares the crushing characteristics of four different types of proppant with three different size ranges that are widely used for hydraulic fracturing in North America. The proppant properties were evaluated using data obtained from a modified crush test. The grain shape before the test, the grain breakage pattern, the stress-strain response of the proppant pack, and the change in particle-size distribution caused by compressive stresses of up to 40 MPa were measured. At the higher compressive stresses, significant differences were observed between the various proppant types as well as for different size ranges for a given proppant type. The results show that the constrained moduli of resin-coated sand and ceramic proppant are 30% higher than those for Jordan sand and Genoa sand. Genoa sand exhibits more grain crushing than Jordan sand, while resin-coated sand and ceramic proppant experienced only minor fracturing at compressive stresses of 40 MPa. The grain shape and size distribution measurements were used to empirically estimate and compare the permeability and fracture conductivity for different proppant packs. Mesh 20/40 and 30/50 ceramic proppants, and mesh 20/40 resin-coated sand are predicted to have twice the permeability of the other proppants at 40 MPa. A good agreement was found between the estimated permeability and published laboratory results for fracture conductivity. This indicates that careful characterization of the particles obtained from a crush test can provide a fast and reliable approach for evaluating proppant pack permeability and fracture conductivity as well as changes in these properties under different compressive stresses without the need to conduct elaborate conductivity tests. Empirical equations quantifying permeability change for four types of proppant with three different sizes are derived with the effect of proppant embedment on fracture conductivity considered. These equations can be incorporated into hydrocarbon production simulations to select proppant types and sizes.

E&P Notes (October 2017)

E&P Notes Researchers Gain Insights Into Microbial Succession in Offshore Wells Joel Parshall, JPT Features Editor Researchers from Shell and Newcastle University in the United Kingdom, in collaboration with the US Department of Energy (DOE) Joint Genome Institute (JGI), have obtained valuable insights into the succession of microbial populations in multiple oil wells drilled in a North Sea field. Findings from the research could influence future industry practices. Microbes play an important part in maintaining the earth’s biogeochemical cycles and are known to have displayed a very successful adaptive capability in extreme subsurface conditions when they are relatively stable. The Shell-Newcastle University research focused on the response of microbes to the disruption of their environment caused by well drilling and production-related activities and the microbial impact on reservoir production. New Study Shows Stanching of Decline in Oil Reserves, Revenue Stephen Whitfield, Senior Staff Writer With the release of Ernst & Young’s (EY) 2017 US oil and gas reserves study, the services firm hosted a presentation in which a panel of its analysts discussed trends among independent and integrated companies within the industry. Along with oil and gas reserves, the panel examined trends in capital expenditures (Capex) for exploration and development activities as well as other performance metrics. A key takeaway from the EY study was that prices are trending lower than in recent history and volatility in price is somewhat subdued. Capex totaled $85.7 billion in 2016, 27% lower than in 2015 and 57% lower than in 2014. The study said that the oil price has stabilized at a “new normal,” and that this stabilization has helped limit the flow of ratings downgrades and reserve revisions from 2015 to 2016. The US Energy Information Administration (EIA) expects the country to see a 4% growth in oil production in 2017. Total Acquires Maersk Oil in $7.5-Billion Deal, Boosts North Sea Presence Pam Boschee, Senior Editor Total will acquire Maersk Oil for $4.95 billion in Total shares and will assume $2.5 billion of Maersk’s debt. The deal will expand Total’s global holdings to approximately 1 billion BOE of 2P/2C reserves, of which more than 80% are in the North Sea. Total said that the combination of its and Maersk’s assets in the North Sea is expected to “generate operational, commercial, and financial synergies” of more than $400 million per year. Closing of the deal is expected in 1Q 2018. Included in the Maersk North Sea holdings are interests in Johan Sverdrup (8.44%) and the Culzean gas condensate field (49.99%). At the end of 2Q, Culzean’s project completion rate was 55%, ahead of the expected 48%. Maersk reported in July that the gas export and condensate pipelines had been laid and all three jackets installed on the field. High-pressure/high-temperature drilling began in July. Production is expected to start in 2019. Demand for Raw Fracturing Sand Set for Healthy Growth Joel Parshall, JPT Features Editor Demand for raw fracturing sand is forecast to increase by more than 4% per year to almost 100 billion pounds in 2021, according to a recently released study by industry research firm, the Freedonia Group. In value terms, raw fracturing sand is expected to grow at a 10% annual rate to more than $3 billion in 2021, which reflects substantial gains in average prices and volume levels. The study, Proppants in North America, presents historical data from 2006, 2011, and 2016. It forecasts to 2021 by type—including raw fracturing sand, resin-coated sand, and ceramic proppant—and market location in pounds and US-dollar values. The study also evaluates key industry players. Raw sand demand is expected to grow in the United States and Canada, with the US being the principal user at a market share of 88% in 2016, the study said. Bidding Interest Drops for Gulf of Mexico Leases Joel Parshall, JPT Features Editor Oil industry interest in obtaining new offshore acreage in the US Gulf of Mexico (GOM) showed a significant decline in the mid-August federal outer continental shelf lease sale, compared with the previous sale in March. US GOM regionwide Lease Sale 249, held by the Bureau of Ocean Energy Management in New Orleans, drew 99 bids from 27 participating companies, with high bids totalling $121 million. The value of all bids received was $137 million for 90 blocks, a decline of 57% in bid value and 45% in block acreage from Central Lease Sale 247 on 22 March. That sale reflected the first increase in industry leasing activity in federal GOM waters in 5 years.

Development of a high-temperature mold process for sand casting with a thin wall and complex shape

A new process has been developed for preparing a mold that can be sustained at a heat treatment of 1000°C, resulting in fabricating cast product having a thin-wall and complex shape. In the new mold process, an inorganic binder composed of tetraethyl orthosilicate and sodium methoxide, and bead powder with a high heat resistance and a low thermal expansion to molten metal were used. The mold sample prepared through the resin-coated sand process using the bead powder showed higher green strength than those through the CO2process using the chamotte sand, while the firing strengths were improved and showed similar values by applying the new mold process using the inorganic binder. In particular, the glassification behavior of the inorganic binder and its phase were not changed even in the mold sample prepared with the recycled bead powder. The thermal expansion of the mold sample was linear and about 0.23% up to 1000°C, indicating that the mold has a superior thermal stability. The actual product, an impeller, was well cast in the mold prepared by the new mold process, indicating that the new mold process is efficient method in improving mold strength.

New Technology Yields Ultrahigh-Strength Proppant

Summary Nearly all of the proppant available on the market today can be classified into one of three tiers—sand, resin-coated sand, or ceramic. The products contained in these three tiers have served the industry well and have typically covered the broad spectrum of applications required by completions engineers. However, with the development of deeper reservoirs and the ongoing look at geothermal and steamflood applications, there now exists a gap in proppant technology. No conventional proppant can provide sufficient conductivity at the 20,000-psi (and higher) closure stresses anticipated in the Lower Tertiary formations in the deep Gulf of Mexico. Similarly, no conventional proppant can adequately withstand the harsh chemical conditions in many geothermal and steamflood applications. The industry has begun to address this gap in performance with the development of higher-strength proppants. One such proppant has been developed and commercialized to meet these challenges. It achieves twice the baseline conductivity of any conventional proppant at these high stresses, and should also provide additional advantages because of increased durability. This paper will review the step-change advancements achieved by this new proppant, including improvements in both raw materials and manufacturing processes. It will present properties never seen before in regard to proppant shape, sizing, and strength. Extensive laboratory testing has been completed and will be presented to demonstrate the superior performance of the proppant in harsh conditions. The paper will also outline the expected applications for this product, including areas in which increased production rates, superior estimated ultimate recovery, lower erosivity, and reduced equipment wear are primary concerns. Field applications are under way to properly assess the implications of these findings. This paper should be beneficial to all completions engineers and production technologists currently working in regions with high-stress applications (≥ 14,000 psi) or other harsh conditions such as those of steamflooding and geothermal applications.