Efficiency Of Hydraulic Fracturing Research Articles

ИССЛЕДОВАНИЕ И АНАЛИЗ МЕТОДОВ ОПРЕДЕЛЕНИЯ ЭФФЕКТИВНОСТИ ПРИМЕНЕНИЯ ТЕХНОЛОГИИ ПРОПАНТНОГО ГИДРОРАЗРЫВА ПЛАСТА

Актуальность. Большинство месторождений ООО «ЛУКОЙЛ-ПЕРМЬ» находятся на завершающей стадии разработки, и на них выполняется большое количество операций гидроразрыва пласта (ГРП). В условиях высокой выработки запасов, обводнения скважин и снижения пластового давления необходимо планировать проведение ГРП на тех скважинах, где может быть получен максимальный прирост дебитов нефти. Цель: разработка методики прогноза дебитов нефти с использованием вероятностно-статистических методов. Объекты: данные по использованию пропантного ГРП на карбонатном В3В4 объекте Батырбайского месторождения. Методы: анализ данных по оценке эффективности ГРП с помощью использования вероятностно-статистических методов. Результаты. С использованием вероятностно-статистического метода построены многомерные математические модели оценки эффективности ГРП, которые позволили определить приросты дебитов нефти. Одним из основных преимуществ вероятностно-статистического метода является то, что все используемые для прогноза показатели, имеющие различные размерности, были переведены в безразмерные величины, что упрощает сопоставительный анализ. Кроме этого, выполнено сравнение полученных приростов дебитов нефти с методом расчета дебита жидкости через удельный коэффициент продуктивности. Выполненный анализ показал, что разработанный вероятностно-статистический метод прогноза обеспечивает более точную сходимость с фактическими данными по приростам дебитов нефти, в отличие от результатов, полученных по методу удельного коэффициента продуктивности. Значения коэффициентов парной корреляции для вероятностно-статистического метода составили по объекту разработки В3В4 – 0,85, тогда как по методу удельной продуктивности, соответственно, – 0,15, что на статистическом уровне подтверждает более высокую эффективность предлагаемого метода.

Study of geological and technological factors on the efficiency of hydraulic fracturing

Using correlation analysis, the authors assess the impact of geological and physical, geological and technological properties on the technological effect in the development of fields using hydraulic fracturing. The dependence of technological effect of hydraulic fracturing from the quality of casing string annulus fixing is also considered. The analysis of technological efficiency of regular technology of hydraulic fracturing in conditions of JSC TATNEFT showed its insufficient level due to the lack of methods which take into account the impact of geological and physical, geological and technological factors. The study of correlation relationship between field results of hydraulic fracturing and reservoir properties established quantitative geological field criteria for its effective use, which allowed to make a more informed choice of objects of impact.

Simplified Model to Estimate Productivity of Horizontal Well with Multistage Hydraulic Fracturing

The article presents a method of approximate evaluation of multistage hydraulic fracturing efficiency in homogeneous single porosity petroleum reservoir. The method considers various types of flow symmetry in certain zones of near-wellbore area. The problem is reduced to one-dimensional differential equation for pressure in fracture and a number of closing analytical formulae. Approximate solution is verified by 3D numerical modeling. Simplified method is applicable both for operational multistage hydraulic fracturing productivity estimation and for mathematical models of petroleum reservoir, especially in large-block modeling.

XRF (X-ray fluorescence) applied to characterization of unconventional Woodford Shale (Devonian, U.S.A.) lateral well heterogeneity

X-ray fluorescence (XRF) was applied to measuring drill cuttings in order to characterize reservoir heterogeneity along a horizontal wellbore that landed in the organic-rich Woodford Shale. The measured XRF data profile which is composed of different paleoenvironmental and sedimentary element proxies were interpreted along with microseismic data distribution patterns from hydraulic fracturing. Three representative microseismic event distribution patterns were selected as demonstrations for reservoir heterogeneity’s impact on hydraulic fracturing efficiency, reflected by the corresponding variation in the XRF profile. This case study indicates that heterogeneity is a non-negligible factor in unconventional shale reservoirs and controls the efficiency of hydraulic fracturing. XRF is not restricted to conduct vertical scale chemostratigraphic characterization on core and outcrop, but also applicable for lateral well heterogeneity characterization near wellbore, which helps optimizing hydraulic fracturing design and ultimately reducing the risk of production failure.

Detecting the propped fracture by injection of magnetic proppant during fracturing

Hydraulic fracturing is key to enhancing the productivity of shale and tight hydrocarbon reservoirs, as well as geothermal resources from hot dry rock. Assessing the range and efficiency of hydraulic fracturing is very important for onsite fracturing operations and decision making on subsequent fracturing plans and well-pattern deployment. The idea of injecting fluid mixed with magnetic material into a formation to detect subterranean structure has been considered for a long time. The detectability of the characteristics of propped fractures using magnetic field measurement is discussed and evaluated with an analytical model. The magnetic proppants synthesized with superparamagnetic nanoparticles should be “silent” during injection and could be activated by an external current. By measuring the magnetic field before and after the fracture was created and the magnetic proppants were magnetized, the magnetic anomalies can be obtained. The result indicates that the magnetic field caused by a fracture filled with magnetic proppants is very weak, so that magnetometers with higher precision and resolution should be used to capture such subtle signal. The higher susceptibility contrast of the magnetic nanoparticles is, the stronger external magnetic induction field could be detected. It is suggested that the superparamagnetic nanomaterial with effective magnetic susceptibility contrast of greater than 0.4–0.5 should be used for fracture monitoring in deep wells. To infer the fracture characteristics with the magnetic anomaly, the ground and adjacent wells’ monitoring practices are recommended.

A Numerical Investigation on the Hydraulic Fracturing Efficiency in Radial Well

In order to investigate the propagation behavior of radial well hydraulic fractures, a low-permeability reservoir in Shengli Oilfield was used as the geologic condition, and a series of numerical simulations of radial well guided hydraulic fracturing were carried out based on a numerical method named Rock Failure Process Analysis 3D. The concept of effective stimulation coefficient was proposed in this paper to illustrate the advantage of radial well fracturing. The results show that compared with the traditional hydraulic fracturing, the effective stimulation coefficient through radial well fracturing is increased by 8% and the effectively stimulated area is increased by 60.6%. The viscosity of the fluid has little effect on the effective stimulation coefficient and effective stimulation area, when compared with the injection rate. The effective stimulation coefficient decreases with the increase of injection rate. And the effectively stimulated area improves with the increase of injection rate. In the process of radial well fracturing, it is possible to reduce the ineffective stimulation and construction costs by reasonably reducing the construction injection rate.

Multipurpose Usage of Magnetic Proppantsduring Shale Gas Exploitation

Abstract Magnetic material may be added to proppant, as the magnetic marker allows to determine the range and efficiency of hydraulic fracturing. However, magnetic proppant may be also used in flowback fluid treatment and monitoring of environmental pollution. As a result of shale gas hydraulic fracturing, large volume of flowback fluid is created. Flow back fluid have similar properties to fracturing fluid, but it is potentially enriched with large amount of salts and organic compounds leached from shale. Magnetic proppant may serve as a heterogeneous catalyst during organic pollutants decomposition. Additionally, in case of leakage and consequently the fracturing fluid pollution, magnetic proppant is placed into the soil environment. It can be detected using magnetometric methods. This article discusses the above-mentioned issues based on the knowledge and experience of the authors and the literature review.

Shear-induced Permeability Evolution of Sandstone Fractures

In underground coal mines, shear-induced changes in regional fluid flow are a major factor causing water inrushes from faults into working faces. Shear slip along preexisting fractures tends to be activated during hydraulic fracturing, and this movement can either enhance or diminish hydraulic fracturing efficiency. To prevent water inrush disasters and further hydraulic fracturing, understanding the evolution of shear-induced permeability in fractures in sedimentary rock is very important. In this study, the evolution of shear-induced permeability in saw-cut sandstone fractures with three different types of surface roughness was investigated by conducting triaxial shear tests and examining the 3-D topography of the unsheared and sheared fracture surfaces. The results allow several important conclusions to be drawn. (1) The permeability of fractures follows a three-stage shear-displacement-dependent evolution. The permeability remains unchanged in the first stable stage. After that, permeability decreases sharply with increasing shear displacement. Finally, the permeability enters a second stable stage. (2) The shear stress versus shear-displacement curves can also be divided into three stages, namely, a stress adjustment stage, a stage of increasing stress, and a stable stage. During the experiments, the fractures always experienced stick-slip shear in the stable stage. The oscillations of the shear stress in the stick-slip stage had a higher frequency for fractures with rougher surfaces. In addition, the rougher surfaces exhibited a greater permeability drop after shearing than that shown by smoother fracture surfaces. (3) The 3-D scanning results imply that the coupled effects of grinding (plus scraping) and sealing lead to decreased permeability. During shearing, the fracture walls grind and scrape against each other resulting in partial flattening of the fracture surface and the production of fault gouge in the fracture. This leads in turn to the flow pathways being partially sealed by crushed mineral grains.

Thermal cooling to improve hydraulic fracturing efficiency and hydrocarbon production in shales

Unconventional hydrocarbon reserves contained in oil and gas shale formations are proving themselves to be abundant sources of current and future energy supply, unlocked through the technologies of horizontal drilling and hydraulic fracturing. Despite the various technology improvements that have buoyed the ”shale revolution” in the last decade, there remain very significant opportunities to further improve hydrocarbon recovery from shales by making hydraulic fracturing more efficient. In this paper, we look into the possibility of stimulating a rock matrix to a higher degree with hydraulic fractures by deliberately cooling down the rock. Cooling reduces in-situ thermal stress, which lowers initiation and propagation pressures of hydraulic fractures. Moreover, when a laterally confined solid undergoes temperature reduction induced by cooling, a thermal stress gradient is developed in the solid body. We perform sensitivity analyses to show that in an in-homogenous shale, this thermal stress gradient can lead to differential contraction of its various mineralogical constituents, which in turn may create thermal cracks. The opening of such cracks increases shale permeability and provides additional pathways for the flow of hydrocarbons, thereby enhancing productivity. Here, we solve the coupled equations of stress, heat transfer and flow using finite element techniques for hydraulic stimulation amplified by cooling. It is shown that thermal cracks in tight formations induced by thermal cooling have the potential to improve the productivity of horizontal wellbores placed in shale by an estimated 16% for the case of methane gas flow through thermally stimulated shale of micro-darcy permeability.

Field Investigation of Hydraulic Fracturing in Coal Seams and Its Enhancement for Methane Extraction in the Southeast Sichuan Basin, China

Hydraulic fracturing is an effective technology for enhancing the extraction of reservoir methane, as proved by field experience and laboratory experiments. However, unlike conventional reservoirs, coal seams had high stress sensitivity and high anisotropy. Therefore, the efficiency of hydraulic fracturing in coal seams needs to be investigated. In this study, hydraulic fracturing was performed at Nantong mine in the southeast Sichuan basin, China. The field investigation indicated that the hydraulic fracturing could significantly enhance the methane extraction rate of boreholes ten times higher than that of normal boreholes in one of the minable coal seams (named #5 coal seam). The performance of hydraulic fracturing in three districts revealed that compared with south flank, the fluid pressure was higher and the injection rate was lower in north flank. The methane extraction rate of south flank was inferior to that of north flank. It indicated hydraulic fracturing had less effect on #5 coal seam in south flank. Moreover, the injection of high-pressure water in coal seams could also drive methane away from boreholes. The methane extraction rate of the test boreholes demonstrated the existence of methane enrichment circles after hydraulic fracturing. It indicated that hydraulic fracturing did act on #5 coal seam in south flank. However, due to the high stress sensitivity of coal seams and the high geo-stress of south flank, the induced artificial fractures in #5 coal seam might close with the decline of the fluid pressure that led to a sharp decline of the methane extraction rate.

The Potential of Nuclear Reactor Technology to Treat Produced/Brackish Water for Oil & Gas Applications

The Potential of Nuclear Reactor Technology to Treat Produced/Brackish Water for Oil & Gas Applications

The Influence of Hydraulic Fracturing on the Estimated Ultimate Recovery

The paper presents the numerical reservoir model constructed to study the influence of hydraulic fracturing on the effective oil recovery. The work of neighboring development wells is also addressed. The paper seeks to examine the way hydraulic fracturing in a development well affects the degree of recovery from the whole pool of the field. To solve this problem, the oil pool model developed by waterflooding is being considered. The paper examines the efficiency of hydraulic fracturing employed in wells at different locations. The study found that well stimulation technique affects the performance of near wells where there is an increase in the water cut of the production and a decrease in the oil rate.

The analysis of the hydraulic fracturing efficiency at the Potochnoe field facility AV1–2

Currently, large deposits of the Russian Federation are in the final stages of development. Taking this into account, the new methods of enhanced oil recovery are required in the final stages of developing formations with hydrocarbon stock hard to recover. The use of hydraulic fracturing allows increasing the degree of oil recovery from flooded formations, optimizing production and prolonging the economically profitable period of development. This paper examines the application of hydraulic fracturing based on the production figures for the facility AV1–2 in the Potochnoe field. The results, obtained on the basis of analysing the formation AV1–2, show that the highest post-frac fluid rate is achieved in the formations of a greater power. The application of large proppant masses allows obtaining higher post-treatment fluid rate. Similarly, the increase of the proppant specific mass results in the growth of the specific post-frac fluid rate.

Technical requirements to laboratory facility for stressed state rock massive spectral-acoustic control method sensitivity depth research if front of a development heading

AnnotationThe article presents the basic requirements for a laboratory facility creation that allows one to investigate the spectral-acoustic monitoring method sensitivity depth when testing the face area stressed state in front of a development heading. These data are necessary for establishing the scope of the spectral-acoustic method use for forecasting the dynamic phenomena in the process of various technological operations performance when mining: forecasting the outburst danger, controlling the anti-outburst measures effectiveness, assessing the anchor support quality and the hard-to-collapse roof directed hydraulic fracturing efficiency and so on. The reported study was funded by Russian Scientific Foundation grant (project No. 17-17-01143).

Forecasting of the hydraulic fracturing efficiency as components of its design optimization

Forecasting of the hydraulic fracturing efficiency as components of its design optimization

Thermal shale fracturing simulation using the Cohesive Zone Method (CZM)

Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

An improved fracture height containment method: artificial gel-barrier technology and its simulation

Overgrowths of hydraulic fracture height occur in reservoirs without stress barriers. It may decrease the efficiency of hydraulic fracturing, pose harm to well production, and increase the possibility of groundwater pollution. Hence, fracture height containment methods are recommended to restrain the overgrowths of fracture height. To enhance the effect of artificial barrier technology, it is improved by replacing the sand or the ceramic used for bridging the fracture tips by gel particles. This innovative technology could be named “artificial gel-barrier technology”. Experiments show that the design of artificial gel-barrier technology is more convenient and controllable, since the dilatability and the gelling performance of the selected gels are mainly controlled by salinity. Experiments also show that the break-through pressure of the gel-barrier is much larger than that of the classical barrier. Numerical simulations reveal that the artificial gel-barrier technology is more helpful and efficient than classical barrier technology. This improved technology has been applied to fracturing operations in Tahe oilfield of China; 73% of these operations were more efficient and the performances of these wells were better than those of adjacent wells.

Experimental analysis of multiple factors on hydraulic fracturing in coalbed methane reservoirs.

Hydraulic fracturing can improve the permeability of coalbed methane (CBM) reservoirs effectively, which is of great significance to the commercial production of CBM. However, the efficiency of hydraulic fracturing is affected by multiple factors. The mechanism of fracture initiation, morphology and propagation in CBM reservoirs is not clear and need to be further explored. Hydraulic fracturing experiment is an accurate tool to explore these mechanisms. The quantity of experimental coal rock is large and processing method is complex, so specimen made of similar materials was applied to replace coal rock. The true triaxial hydraulic fracturing experimental apparatus, 3D scanning device for coal rock section were applied to carry out hydraulic fracturing experiment. The results show that the initiation pressure is inversely proportional to the horizontal stress difference (Δσ) and positively related to fracturing fluid injection rate. When vertical stress (σv) is constant, the initiation pressure and fracture width decrease with the increasing of Δσ. Natural fractures can be connected by main fracture when propagates perpendicular to the direction of minimum horizontal stress (σh), then secondary fractures and fracture network form in CBM reservoirs. When two stresses of crustal stress are close and far different from the third one, the fracture morphology and propagation become complex. Influenced by perforations and filtration of fracturing fluid in specimen, fracturing fluid flows to downward easily after comparing horizontal well fracturing with vertical well fracturing. Fracture width increases with the decreasing of elastic modulus, the intensity of fracture is positively related with the elastic modulus of coal rock. The research results can provide theoretical basis and technical support for the efficient development of CBM.

THE SIGNIFICANCE OF GEOLOGICAL DATA AT HYDRAULIC FRACTURING PLANNING

Scientific and methodological aspects of the development of oil and gas fields at the use of hydraulic fracturing have been considered. The causes of unsatisfactory results at hydraulic fracturing, and also factors to be taken into account when choosing a well and a bed for hydraulic fracturing have been analyzed. It has been established that geological factors (in-place permeability, skin-factor, bed formation pressure, bed formation litho­logy, thickness, mechanical reservoir characteristics etc.) at hydraulic fracturing planning have a main impact on the hydraulic fracturing efficiency, and the errors introduced at the study of these factors are predetermined either by the insufficient study of collecting and host properties of the bed formation, or by the insufficient study of a trap.

Оценка эффективности гидроразрыва пласта в добывающих скважинах и детализация по критериям применимости

Оценка эффективности гидроразрыва пласта в добывающих скважинах и детализация по критериям применимости