Geologic characteristics,exploration and production progress of shale oil and gas in the United States:An overview

We present a systematic summary of the geological characteristics,exploration and development history and current state of shale oil and gas in the United States.The hydrocarbon-rich shales in the major shale basins of the United States are mainly developed in six geological periods:Middle Ordovician,Middle-Late Devonian,Early Carboniferous(Middle-Late Mississippi),Early Permian,Late Jurassic,and Late Cretaceous(Cenomanian-Turonian).Depositional environments for these shales include intra-cratonic basins,foreland basins,and passive continental margins.Paleozoic hydrocarbon-rich shales are mainly developed in six basins,including the Appalachian Basin(Utica and Marcellus shales),Anadarko Basin(Woodford Shale),Williston Basin(Bakken Shale),Arkoma Basin(Fayetteville Shale),Fort Worth Basin(Barnett Shale),and the Wolfcamp and Leonardian Spraberry/Bone Springs shale plays of the Permian Basin.The Mesozoic hydrocarbon-rich shales are mainly developed on the margins of the Gulf of Mexico Basin(Haynesville and Eagle Ford)or in various Rocky Mountain basins(Niobrara Formation,mainly in the Denver and Powder River basins).The detailed analysis of shale plays reveals that the shales are different in facies and mineral components,and"shale reservoirs"are often not shale at all.The United States is abundant in shale oil and gas,with the in-place resources exceeding 0.246×10^(12)t and 290×10^(12)m^(3),respectively.Before the emergence of horizontal well hydraulic fracturing technology to kick off the"shale revolution",the United States had experienced two decades of exploration and production practices,as well as theory and technology development.In 2007-2023,shale oil and gas production in the United States increased from approximately 11.2×10^(4)tons of oil equivalent per day(toe/d)to over 300.0×10^(4)toe/d.In 2017,the shale oil and gas production exceeded the conventional oil and gas production in the country.In 2023,the contribution from shale plays to the total U.S.oil and gas production remained above 60%.The development of shale oil and gas has largely been driven by improvements in drilling and completion technologies,with much of the recent effort focused on“cube development”or“co-development”.Other efforts to improve productivity and efficiency include refracturing,enhanced oil recovery,and drilling of“U-shaped”wells.Given the significant resources base and continued technological improvements,shale oil and gas production will continue to contribute significant volumes to total U.S.hydrocarbon production.

Shale oil and gas exploitation in China:Technical comparison with US and development suggestions

The shale oil and gas exploitation in China is technically benchmarked with the United States in terms of development philosophy,reservoir stimulation treatment,fracturing parameters,fracturing equipment and materials,oil/gas production technology,and data/achievements sharing.It is recognized that the shale oil and gas exploitation in China is weak in seven aspects:understanding of flow regimes,producing of oil/gas reserves,monitoring of complex fractures,repeated stimulation technology,oil/gas production technology,casing deformation prevention technology,and wellbore maintenance technology.Combined with the geological and engineering factors of shale oil and gas in China,the development suggestions of four projects are proposed from the macro-and micro-perspective,namely,basic innovation project,exploitation technology project,oil/gas production stabilization project,and supporting efficiency-improvement project,so as to promote the rapid,efficient,stable,green and extensive development of shale oil and gas industry chain and innovation chain and ultimately achieve the goal of“oil volume stabilizing and gas volume increasing”.

Distribution and treatment of harmful gas from heavy oil production in the Liaohe Oilfield, Northeast China

The distribution and treatment of harmful gas （H2S） in the Liaohe Oilfield, Northeast China, were investigated in this study. It was found that abundant toxic gas （H2S） is generated in thermal recovery of heavy oil. The H2S gas is mainly formed during thermochemical sulfate reduction （TSR） occurring in oil reservoirs or the thermal decomposition of sulfocompounds （TDS） in crude oil. H2S generation is controlled by thermal recovery time, temperature and the injected chemical compounds. The quantity of SO4^2- in the injected compounds is the most influencing factor for the rate of TSR reaction. Therefore, for prevention of H2S formation, periodic and effective monitoring should be undertaken and adequate H2S absorbent should also be provided during thermal recovery of heavy oil. The result suggests that great efforts should be made to reduce the SO4^2- source in heavy oil recovery, so as to restrain H2S generation in reservoirs. In situ burning or desulfurizer adsorption are suggested to reduce H2S levels. Prediction and prevention of H2S are important in heavy oil production. This will minimize environmental and human health risks, as well as equipment corrosion.

Progress and prospects of oil and gas production engineering technology in China

This paper summarizes the important progress in the field of oil and gas production engineering during the"Thirteenth Five-Year Plan"period of China,analyzes the challenges faced by the current oil and gas production engineering in terms of technological adaptability,digital construction,energy-saving and emission reduction,and points out the future development direction.During the"Thirteenth Five-Year Plan"period,series of important progresses have been made in five major technologies,including separated-layer injection,artificial lift,reservoir stimulation,gas well de-watering,and workover,which provide key technical support for continuous potential tapping of mature oilfields and profitable production of new oilfields.Under the current complex international political and economic situation,oil and gas production engineering is facing severe challenges in three aspects:technical difficulty increases in oil and gas production,insignificant improvements in digital transformation,and lack of core technical support for energy-saving and emission reduction.This paper establishes three major strategic directions and implementation paths,including oil stabilization and gas enhancement,digital transformation,and green and low-carbon development.Five key research areas are listed including fine separated-layer injection technology,high efficiency artificial lift technology,fine reservoir stimulation technology,long term gas well de-watering technology and intelligent workover technology,so as to provide engineering technical support for the transformation,upgrading and high-quality development of China’s oil and gas industry.

Achievements and future work of oil and gas production engineering of CNPC

This paper summarizes the latest achievements and technological progress in oil and gas production engineering of China National Petroleum Corporation(CNPC) and discusses the main four challenges faced: developing low quality resource at low oil price; keeping stable production of mature oilfields when well oil production drops year by year; low systematic efficiency, high cost, prominent environmental protection issue and short of technological strategy for high water cut ratio and high oil recovery ratio oilfields; and lacking of high level horizontal well drilling and completion technology to develop unconventional and deep reservoirs. Three technological development directions to address these challenges are put forward: developing fracture controlling stimulation and well factory to produce low quality resource economically, developing re-fracturing technology for old wells in mature oilfields, promoting the fourth generation separate layer water injection technology to stabilize the production of mature oilfields; innovating new technologies of water flooding with nano-material, injecting and producing through one well.

Technological progress and development directions of PetroChina overseas oil and gas field production

This study reviews the development history of PetroChina’s overseas oil and gas field development technologies, summarizes the characteristic technologies developed, and puts forward the development goals and technological development directions of overseas business to overcome the challenges met in overseas oil and gas production. In the course of PetroChina’s overseas oil and gas field production practice of more than 20 years, a series of characteristic technologies suitable for overseas oil and gas fields have been created by combining the domestic mature oil and gas field production technologies with the features of overseas oil and gas reservoirs, represented by the technology for high-speed development and stabilizing oil production and controlling water rise for overseas sandstone oilfields, high efficiency development technology for large carbonate oil and gas reservoirs and foamy oil depletion development technology in use of horizontal wells for extra-heavy oil reservoirs. Based on in-depth analysis of the challenges faced by overseas oil and gas development and technological requirements, combined with the development trends of oil and gas development technologies in China and abroad, overseas oil and gas development technologies in the future are put forward, including artificial intelligence reservoir prediction and 3 D geological modeling, secondary development and enhanced oil recovery(EOR) of overseas sandstone oilfields after high speed development, water and gas injection to improve oil recovery in overseas carbonate oil and gas reservoirs, economic and effective development of overseas unconventional oil and gas reservoirs, efficient development of marine deep-water oil and gas reservoirs. The following goals are expected to be achieved: keep the enhanced oil recovery(EOR) technology for high water-cut sandstone oilfield at international advanced level, and make the development technology for carbonate oil and gas reservoirs reach the international advanced level, and the development technologies for unconventional and marine deep-water oil and gas reservoirs catch up the level of international leading oil companies quickly.

Methodology and Equations of Mineral Production Forecast. Part II. The Fundamental Equation. Crude Oil Production in USA

The fundamental equation of mineral production allows to model and design the dynamics of mineral production, however complex they are or could be. It considers not only the case of a constant production to reserves ratio for given intervals of time, but with a piecewise approach, it is also enabled to account the variation on time of this ratio. With a constant production to reserves ratio, the limit expression of the fundamental equation takes the form of an Erlang distribution with a fixed shape parameter. The rate parameter equals the scale factor. The discrete piecewise version, instead of considering the reserves and the production to reserves ratio being constant through certain intervals of time, updates both variables by units of time. This version, using either lineal or non lineal functions for the variables involved, let to model known production profiles or to forecast them by experimental design. The Hubbert’s linearization updated with recent data and the p-box method applied to determine ultimate recovery of U.S. crude oil reserves indicate official accounts underestimate them. The analysis of the ideal model of production based on Hubbert’s linearization and curve, can be made by decomposing it in the distribution with time of the reserves and of the production to reserves ratio. The distribution of reserves with time is synchronized for both the ideal Hubbert’s curve and real profiles, disregarding whether they match or not. The departure of real profiles from the ideal Hubbert’s curve lies on the differences or correspondences of the distribution with time of the production to reserves ratio. The MonteCarlo simulation applied to forecast US crude oil production for the next five years points to a slow decline, with average annual yields presenting a difference lower than 10% between the start and the end of the simulation.

1995──A Year of Continuous Increase in Oil and Gas Production

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Environmental Impacts of Oil and Gas Production in Nigeria

Energy and environment are essential for sustainable development of any nation hence the need for effective and efficient energy production. UNFCCC reports indicate that those who are least responsible for climate change are the most vulnerable to its projected impact and the masses are the ones affected by environmental degradation and lack of access to clean and affordable energy services. This paper therefore addresses the effects of these issues, some forms of energy production in Nigeria and the effects on our environment and how it can be effectively managed through innovative policies and partnership with organizations that can help pilot projects that will build a sustainable energy.

Multistring analysis of wellhead movement and uncemented casing strength in offshore oil and gas wells

This paper presents a theoretical method and a finite element method to describe wellhead movement and uncemented casing strength in offshore oil and gas wells.Parameters considered in the theoretical method include operating load during drilling and completion and the temperature field,pressure field and the end effect of pressure during gas production.The finite element method for multistring analysis is developed to simulate random contact between casings.The relevant finite element analysis scheme is also presented according to the actual procedures of drilling,completion and gas production.Finally,field cases are presented and analyzed using the proposed methods.These are four offshore wells in the South China Sea.The calculated wellhead growths during gas production are compared with measured values.The results show that the wellhead subsides during drilling and completion and grows up during gas production.The theoretical and finite element solutions for wellhead growth are in good agreement with measured values and the deviations of calculation are within 10％.The maximum von Mises stress on the uncemented intermediate casing occurs during the running of the oil tube.The maximum von Mises stress on the uncemented production casing,calculated with the theoretical method occurs at removing the blow-out-preventer （BOP） while that calculated with the finite element method occurs at gas production.Finite element solutions for von Mises stress are recommended and the uncemented casings of four wells satisfy strength requirements.

Distributed optical fiber acoustic sensor for in situ monitoring of marine natural gas hydrates production for the first time in the Shenhu Area,China

The distributed acoustic sensor(DAS)uses a single optical cable as the sensing unit,which can capture the acoustic and vibration signals along the optical cable in real-time.So it is suitable for monitoring downhole production activities in the process of oil and gas development.The authors applied the DAS system in a gas production well in the South China Sea for in situ monitoring of the whole wellbore for the first time and obtained the distributed acoustic signals along the whole wellbore.These signals can clearly distinguish the vertical section,curve section,and horizontal production section.The collected acoustic signal with the frequency of approximately 50 Hz caused by the electric submersible pump exhibit a signal-to-noise ratio higher than 27 dB.By analyzing the acoustic signals in the production section,it can be located the layers with high gas production rates.Once an accurate physical model is built in the future,the gas production profile will be obtained.In addition,the DAS system can track the trajectory of downhole tools in the wellbore to guide the operation.Through the velocity analysis of the typical signals,the type of fluids in the wellbore can be distinguished.The successful application of the system provides a promising whole wellbore acoustic monitoring tool for the production of marine gas hydrate,with a good application prospect.

Assessment of Uinta Basin Oil and Natural Gas Well Pad Pneumatic Controller Emissions

In the fall of 2016, a field study was conducted in the Uinta Basin Utah to improve information on oil and natural gas well pad pneumatic controllers (PCs) and emission measurement methods. A total of 80 PC systems at five oil sites (supporting six wells) and three gas sites (supporting 12 wells) were surveyed, and emissions data were produced using a combination of measurements and engineering emission estimates. Ninety-six percent of the PCs surveyed were low actuation frequency intermittent vent type. The overall whole gas emission rate for the study was estimated at 0.36 scf/h with the majority of emissions occurring from three continuous vent PCs (1.1 scf/h average) and eleven (14%) malfunctioning intermittent vent PC systems (1.6 scf/h average). Oil sites employed, on average 10.3 PC systems per well compared to 1.5 for gas sites. Oil and gas sites had group average PC emission rates of 0.28 scf/h and 0.67 scf/h, respectively. This difference was due in part to differing site selection procedures used for oil and gas sites. The PC system types encountered, the engineering emissions estimate approach, and comparisons to measurements are described. Survey methods included identification of malfunctioning PC systems and emission measurements with augmented high volume sampling and installed mass flow meters, each providing a somewhat different representation of emissions that are elucidated through example cases.

Nuclear magnetic resonance study of the formation and dissociation process of nature gas hydrate in sandstone

In this work,the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance(NMR)relaxation time(T_(2))and 2D imaging measurement.The result shows that the intensity of T_(2) spectra and magnetic resonance imaging(MRI)signals gradually decreases in the hydrate formation process,and at the same time,the T_(2) spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate.The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity.Significantly,for the sample with lower porosity and higher argillaceous content,the intensity of the T_(2) spectra also shows a trend of a great decrease in the hydrate formation process,which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content.The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.

Erratum to “Assessment of Uinta Basin Oil and Natural Gas Well Pad Pneumatic Controller Emissions” [Journal of Environmental Protection, 2017, 8, 394-415]

In the fall of 2016, a field study was conducted in the Uinta Basin Utah to improve information on oil and natural gas well pad pneumatic controllers (PCs) and emission measurement methods. A total of 80 PC systems at five oil sites (supporting six wells) and three gas sites (supporting 12 wells) were surveyed, and emissions data were produced using a combination of measurements and engineering emission estimates. Ninety-six percent of the PCs surveyed were low actuation frequency intermittent vent type. The overall whole gas emission rate for the study was estimated at 0.36 scf/h with the majority of emissions occurring from three continuous vent PCs (1.1 scf/h average) and eleven (14%) malfunctioning intermittent vent PC systems (1.6 scf/h average). Oil sites employed, on average 10.3 PC systems per well compared to 1.5 for gas sites. Oil and gas sites had group average PC emission rates of 0.28 scf/h and 0.67 scf/h, respectively. This difference was due in part to differing site selection procedures used for oil and gas sites. The PC system types encountered, the engineering emissions estimate approach, and comparisons to measurements are described. Survey methods included identification of malfunctioning PC systems and emission measurements with augmented high volume sampling and installed mass flow meters, each providing a somewhat different representation of emissions that are elucidated through example cases.

The Degradation and Pollution of Soils on the Territory of the Kovykta Gas Condensate Field

In this paper, research results from the time interval 2002-2012 are used to give an account of the chemical composition of soils on the territory of the Kovykta gas condensate field. The findings presented provide a better understanding of the ecological state of soil cover, its resilience to anthropogenic impacts, and its possible disturbance caused by the drilling pad construction activity, and by the laying of geophysical profiles. An analysis of soil pollution for the study territory generally showed that the soils are polluted with chemical elements which refer to toxicity classes： Pb, Cu, Ni, Cr, Ba and Mn. High levels ofoil products were detected near boreholes. Strong mineralization was recorded in the soil near borehole. It has a chloride-sodium chemical composition. As a result of the construction of foundation pits, recesses, ditches and earth embankments, the soil is totally destroyed, and rock outcrops show up. Disturbances of the sod cover due to road construction or even by all-terrain vehicles in these extreme conditions entail an accelerated development of linear erosion to form scours and gullies. Elimination of the canopy layer leads to an increase in surface heating, and to an acceleration of permafrost thawing. Swamping is accelerated on negative relief forms due to the increased entry of melt waters.

Hydrocarbon-Based Contaminants in Drinking Water Sources and Shellfish in the Soku Oil and Gas Fields of South-South Nigeria

Environmentally unfriendly Oil exploration activities have been ongoing in the Soku area of the Niger Delta of Nigeria since 1956. This study evaluated the concentration of hydrocarbons and heavy metals in Shellfish and drinking water sources in the study area. It revealed the absence (<0.001 mg/l) of most heavy metals (Ni, Ch, Cd, Pb mg/l) in the water column;a high concentration of the major ion composition of seawater (sulphates 5 - 1018;calcium 0.502 - 53.502;sodium 1.247 - 63.337;potassium 0.508 - 102.745;magnesium 0.354 - 42.574 mg/l);and high PAHs (<0.001 - 0.032 mg/l) levels occurring above WHO limits (0.007 mg/l) with some risk of exposure to cancer. Results from the analysis of shellfish showed that concentrations of chromium and zinc were below permissible limits while cadmium concentrations were slightly above permissible limits of the European Community. Nickel and lead were above permissible limits in the fish samples in all standards while PAHs occurred at the cancer risk levels of 10?6. A review of the public health situation in the Soku area with a view to understanding current trends, sources of perturbations and preferable solutions to the potential public health challenges raised in this study is hereby recommended. Also, this study recommends that relevant agencies and developmental partners should launch a national drive to create awareness among people/environmental/public health professionals’/health workers/administrators on this regional concern.