Unconventional Oil Production Research Articles

Revising the effectiveness of thermal method application for unconventional bitumen oil production stimulation

A theoretical model of petroleum reservoir engineering process with high viscosity oil using the technology of double horizontal wells is proposed. Numerical solutions of the problem in a two-dimensional formulation are obtained. With this method of producing high viscosity oil the efficiency of oil reservoir development can be increased by ensuring uniform heating of the developed zone of the field. The proposed model allows us to trace the two-dimensional picture of oil filtration in the reservoir and investigate the main regularities of the process. The costs for oil reservoir heating, flow rate development and changes in the mass of pumped oil in the initial period of well operation are determined. The obtained solutions for a long stretch of time were extrapolated.

Chemical composition of Bakken crude oil burn residue: Environmental relevance following train derailment fires

Shipments of Bakken crude oil by rail have increased in concert with the production of unconventional crude oil in the Williston Basin over the past 10 years, during which time multiple fiery train derailments resulted in tragic loss of life and/or environmental impacts. In this study the compositions of Bakken oil burn residues from a derailment fire(s) are compared to fresh and laboratory-evaporated Bakken crude oil. The absolute and hopane-normalized concentrations of n-alkanes, unsubstituted and substituted PAHs, and petroleum biomarkers and their percent depletions and enrichments (relative to hopane) are reported. Bakken oil burn residues lost 67–78% of their total chromatographable mass (C5 to C44) and exhibit chemical trends distinct from naturally-evaporated oil, including (1) the shape of their UCM profiles, (2) depletion of n-alkanes up to (at least) n-C30, (3) enrichment of priority pollutant (pyrogenic) PAHs, specifically favoring PAH isomers containing three or more linear aromatic rings (anthracene or benz[a]anthracene) or 5-member rings (fluoranthene or indeno[1,2,3-c,d]pyrene), and (4) depletion of some lower boiling petroleum biomarkers (C23-C25 tricyclic terpanes). Despite relative enrichment of most priority pollutant PAHs the absolute concentrations of both total PAH (TPAH50) and priority pollutant PAH (PPAH16) in the burn residues were depleted 69–78% and 41–48%, respectively, compared to fresh Bakken oil. These results demonstrate the changes and range of compositions among fresh, evaporated, and variably-combusted residues of Bakken crude oil, the latter of which are important in assessing the potential effect(s) of burn residues on the environment proximal to train derailment fires.

Unconventional Oil and Natural Gas Production, Health, and Social Perspectives on Fracking

A growing body of literature suggests that unconventional oil and natural gas (UOG) production-related pollution is harmful to human and environmental health. Despite evidence linking UOG methods s...

Comparative evaluation of multi-basin production performance and application of spatio-temporal models for unconventional oil and gas production prediction

Modern data analytic techniques, statistical and machine-learning algorithms have received widespread applications for solving oil and gas problems. As we face problems of parent–child well interactions, well spacing, and depletion concerns, it becomes necessary to model the effect of geology, completion design, and well parameters on production using models that can capture both spatial and temporal variability of the covariates on the response variable. We accomplish this using a well-formulated spatio-temporal (ST) model. In this paper, we present a multi-basin study of production performance evaluation and applications of ST models for oil and gas data. We analyzed dataset from 10,077 horizontal wells from 2008 to 2019 in five unconventional formations in the USA: Bakken, Marcellus, Eagleford, Wolfcamp, and Bone Spring formations. We evaluated well production performance and performance of new completions over time. Results show increased productivity of oil and gas since 2008. Also, the Bakken wells performed better for the counties evaluated. We present two methods for fitting spatio-temporal models: fixed rank kriging and ST generalized additive models using thin plate and cubic regression splines as basis functions in the spline-based smooths. Results show a significant effect on production by the smooth term, accounting for between 60 and 95% of the variability in the six-month production. Overall, we saw a better production response to completions for the gas formations compared to oil-rich plays. The results highlight the benefits of spatio-temporal models in production prediction as it implicitly accounts for geology and technological changes with time.

Pore Space Property

Through modern technology, we can use the void pore space of underground rock formations for a growing number of socially beneficial purposes. These run the gamut from unconventional oil and gas production to climate change mitigation. The common law of property and tort, however, has struggled to keep up. Significant questions remain about the nature of property rights in pore space. Of particular interest are the limits, if any, on an owner’s right to use pore space for beneficial purposes when it extends beneath the land of another. For example, may A hydraulically fracture an oil well on her property if the fractures extend beneath B’s land? May C store anthropogenic carbon dioxide for climate change mitigation in a common reservoir that extends beneath the land of D, E, F, and G if they do not consent? If so, what if any compensation does C owe to the others? These and similar scenarios pose urgent questions for a wide range of landowners, industries, environmental interests, courts, and policymakers across the nation. This Article searches for answers to these pressing questions in the doctrinal histories of similar common pool natural resources. The Article reviews the development of common law rights in water and oil and gas to synthesize lessons for shaping the content and limits of rights in pore space. Then, applying these lessons to the current state of pore space rights, the Article explains that rights in pore space are established by a default rule of prior use and are absolute, subject to little if any limitation. As demand for the resource continues to grow, however, owners and, ultimately, courts will likely search for ways to limit the absolute extent of pore space rights to avoid a tragedy of the pore space commons. In searching for doctrinal mechanisms to make pore space rights limited, or correlative, instead of absolute, the Article predicts that courts will be tempted to choose between establishing limits by strict, formalist rules of proportionality (which favor certainty), on the one hand, and instrumentalist, utilitarian standards of reasonable use (which favor development of the resource), on the other. This Article, however, identifies an underexplored doctrine from oil and gas law that would define the limits of pore space rights without resort to purely instrumentalist or formalist doctrines. The “fair-opportunity doctrine” articulated here would permit an owner to use any quantity of pore space anywhere in a common reservoir, so long as it does not interfere with the lawful existing operations of other owners, or deprive other owners of a fair opportunity to either participate in the proposed operations or conduct like operations from their respective land.

Brittleness Evaluation of Chang7 Reservoir in Longdong Area Based on Mechanical Parameters and Stress-strain

Brittleness determines the effect of reservoir fracturing and is the key to improve unconventional oil and gas production. In order to accurately understand the brittleness and fracture parameters of the reservoir, triaxial compression test and stress-strain analysis were carried out on the Chang 7 rock samples from well N-1 and well Z-1 in Longdong area of Ordos basin, based on which, the brittleness index was calculated. The results show that the brittleness index calculated by stress-strain method is 51.95%-52.96% and by mechanical parameters method is 57.2%-57.5%; the brittleness index is high, indicating that chang7 reservoir in Longdong area has high brittleness, which is conducive to later fracturing.

Study on Rock Mechanics Parameters of Benxi Formation in Yanchang gas field, Ordos Basin

Rock mechanics parameters can reflect the brittleness of the formation and determine the effect of reservoir fracturing, and they are very important for improving unconventional oil and gas production. Triaxial compression test and acoustic pulse test are carried out in the sandstone samples of Benxi formation in Yanchang gas field of Ordos basin in order to obtain the accurate mechanical properties of the formation. The static elastic modulus ranges from 23.74 GPa to 32.46 GPa and the static Poisson’s ratio ranges from 0.181 to 0.239 in triaxial compression test. The dynamic elastic modulus ranges from 33.18 GPa to 52.56 GPa and the dynamic Poisson’s ratio ranges from 0.26 to 0.30 in acoustic wave test. It can be seen that the dynamic parameters are generally larger than the static parameters, and the relation between them is Es = 0.3624Ed + 11.865, R2 = 0.8119; μs = 1.243μd - 0.0911, R2 = 0.7267.The relation between dynamic and static rock mechanics parameters provides a reliable parameter basis for the study of mechanical properties, brittleness and fracturing.

Book Review: Regulating Water Security in Unconventional Oil and Gas

Regulating Water Security in Unconventional Oil and Gas is a collection of articles authored by professionals from disciplines as diverse as agriculture, zoology, law, and economics. The book takes a multidisciplinary look at how issues related to water for unconventional oil and gas production affect water security of a nation, state, community, or sector of industry—and possible pathways toward regulations that balance economic development with the human right to water. The authors examine what other regions have been experiencing to illustrate some of the common difficulties and differing perspectives, challenges, and solutions being attempted. Authors’ contributions are presented in four parts, making the dense subject matter digestible. Citation: Foster J. 2020. Book Review: Regulating water security in unconventional oil and gas. Texas Water Journal. 11(1):61-63. Available from: https://doi.org/10.21423/twj.v11i1.7114.

Understanding Self-Rated Health and Unconventional Oil and Gas Development in Three Colorado Communities

Domestic, onshore oil and gas production has increased substantially in the United States in the last ∼20 years, creating a range of positive and negative impacts on communities. In this paper, we add to the growing literature on unconventional oil and gas production (a.k.a., “fracking”) and well-being by evaluating the association between self-reported stress induced by local oil and gas development and subjective well-being in the form of self-rated health. We also ask how the intensity of local drilling and trust in regulators influences self-rated health. Using novel survey data, we compare three Colorado communities with differential amounts of oil and gas development. Results from ordinal logistic regression models suggest that living in a community that hosts extraction is associated with lower self-rated health and that stress from local oil and gas operations is associated with lower self-rated health. To some degree, trust in regulators seems to improve self-rated health. We discuss implications for research and policy.

Impact of maturity on producible shale oil volumes in the Silurian (Llandovery) hot shales of the northern Arabian plate, southeastern Turkey

The Silurian (Llandovery) hot shales in southeastern Turkey have excellent source rock potential, with an average total organic carbon (TOC) of 5.9 wt. % and generation potential values of 14.9 mg HC/g TOC. The hot shales contain type II organic matter and demonstrate oil and secondary gas generation potential. Hydrogen indices range from 36 to 510 mg HC/g TOC, depending on maturity. The hot shales in the Gulf Kevan 1 and Turkish Petroleum (TP) Dogan 1 wells are immature–early mature with a vitrinite reflectance equivalent (Requ) of 0.58%–0.76%. The hot shales in the TP Soguktepe 1 and TP K. Migo 2 wells are mature and in the oil window at 0.78%–0.92% Requ. The hot shales are interpreted to be in the wet gas–condensate maturity window with 1.08%–1.30% Requ in the TP G. Hazro 2 and TP-Arco Abdulaziz 1 wells. Corrected (evaporation loss restored using oil API gravity values) oil saturation index values (OSIc) within the Gulf Kevan 1, TP Dogan 1, and TP-Arco Abdulaziz 1 wells are less than 100 mg HC/g TOC, which indicates that unconventional commercial oil production is not probable. The OSIc values of the mature hot shales at the TP Soguktepe 1, TP K. Migo 2, and TP G. Hazro 2 wells all exceed 100 mg HC/g TOC, indicating potentially producible oil and wet gas condensate. Thus, producible oil and wet gas condensate in the hot shale play appear present in areas that have been assessed as having between 0.8% and 1.1% Requ.

Thermo-poroelasticity under constant fluid flux and localized heat source

Coupled thermo-hydraulic-mechanical behavior of saturated porous media with low permeability is of crucial significance to multiple operations including thermal treatment for declogging wellbores, thermal fracturing during production of unconventional shale oil, radioactive-waste disposal, and soft tissue and tumor growth. This work presents new thermo-poroelastic solutions for an isotropic medium subjected to a constant fluid flux and a localized heat source, incorporating two novel components: (a) transient flow transfer between the source and the embedding layer, thus incorporating the temporal thermo-poroelastic changes in the stress state adjacent to the source; and (b) vertical confinement effects on the mechanical response of the target zone, governed by the stiffness of the sealing media using the Winkler model approximation. The Westerly Granite is selected to assess the thermo-poroelastic alterations induced under the imposed fluid flux and heat loads. Results reveal generation of short-term thermal-induced pore pressures subsequent to injection initiation which otherwise cannot be predicted using current solutions. The new solutions capture higher thermal induced pore pressures and a more rapid dissipation under a higher heat transition rate between the source and the target zone. A compassion between the response of the porous layer under constant fluid flux and localized heat source, versus localized heat and flow sources reveals the former loading to be the most effective for localized thermal treatment as it results in: notably higher thermal-induced pore pressures, the maximum thermal-induced pressures to occur in the source vicinity; and particularly slower dissipation of the thermal-induced pore pressures. The stress paths demonstrate slight initial dilation before compaction under the latter loading; while the former results in an initial compaction with higher deviatoric stresses proceeded by dilation once the thermal-induced pore pressures tend to dissipate. Stress paths reveal the vertical confinement to remarkably impact the response of a porous layer. Higher compaction is generated under higher vertical confinement. In case of a mechanically free source-medium interface, lower vertical confinement gives rise to higher deviatoric stresses and lower mean stresses during the initial compaction phase, in addition to causing the formation to undergo dilation much sooner compared to when higher confinement is applied. For a mechanically fixed boundary setting, higher deviatoric stresses are generated under higher vertical confinements.

Impact of local thermal non-equilibrium on temporal thermo-hydro-mechanical processes in low permeable porous media

The thermo-hydraulic-mechanical (THM) response of low permeable media is of crucial significance in thermal fracturing for production of unconventional shale oil, enhanced geothermal systems, and waste disposal. During such processes, pore pressures and stresses change in a spatiotemporal manner due to hydraulic and thermal loadings. From the viewpoint of the energy balance equation, the available theoretical studies can be classified as local thermal equilibrium (LTE), and local thermal non-equilibrium (LTNE) models. LTE models consider identical temperature for different phase of the porous system. LTNE models allow different temperature variations in solid and fluid phases of a porous medium. Current LTNE studies are weakly-coupled – not incorporating thermo-osmosis. This paper presents novel coupled LTNE thermo-poroelastic solutions in a transversely isotropic saturated porous medium, incorporating thermo- osmosis effect. Solutions are obtained for permeable and impermeable boundaries. Thermo-osmosis is found to have a very different effect in case of LTNE versus LTE, resulting in a fundamentally different THM response. LTNE effect analysis reveals different THM responses under different heat transfer properties at the solid-fluid interface in low permeable strata.

Spatiotemporal and stratigraphic trends in salt-water disposal practices of the Permian Basin, Texas and New Mexico, United States

Subsurface disposal of salt water coproduced with oil and gas has become a critical issue in the United States because of linkages with induced seismicity, as seen in Oklahoma and northcentral Texas. Here, we assess the spatiotemporal and stratigraphic variations of salt-water disposal (SWD) volumes in the Permian Basin. The results of this analysis provide critical input into integrated assessments needed for handling of produced water and for emerging concerns, such as induced seismicity. Wellbore architecture, permits, and disposal volumes were compiled, interpreted for disposal intervals and geologic targets, and summarized at formation, subregion, a 100-mi2 (260-km2) area, and monthly volumes for the years 1978–2016. Geologic targets were interpreted by intersecting the disposal intervals with gridded stratigraphic horizons and by reviewing well logs where available. A total of 30 billion bbl (∼5 trillion L) were disposed into 73 geologic units within 6 subregions via 8201 active SWD wells for 39 yr. Most disposal occurred in the Midland Basin and Central Basin Platform (CBP) over the first 34 yr but shifted from the CBP to the Delaware Basin over the last 5 yr (2011–2016) with the expansion of unconventional oil and gas production. Approximately half of the salt water is disposed above the major unconventional reservoirs into Guadalupian-aged formations, raising concerns of overpressuring and interference with production. Operators are exploring deeper SWD targets; however, proximity to crystalline basement poses concerns for high drilling costs and the potential for induced seismicity by reactivation of deep-seated faults.

Spatial variability of produced-water quality and alternative-source water analysis applied to the Permian Basin, USA

Interest in both environmental impact and potential beneficial uses of produced water (PW) has increased with growth in unconventional oil and gas production, especially in semi-arid regions, e.g. the Permian Basin, the most productive tight-oil region in the USA. Characterization of PW compositional variability is needed to evaluate environmental impact, treatment, and reuse potential. Geochemical variability of PW from Guadalupian (Middle Permian) to Ordovician formations was statistically and geostatistically evaluated in the western half of the Permian Basin (Delaware Basin, Central Basin Platform, and Northwest Shelf) using the US Geological Survey’s Produced Waters Geochemical Database and the New Mexico Water and Infrastructure Data System. Mean total dissolved solids (TDS) of PW increased with depth in the Delaware Basin and Central Basin Platform to the Delaware and Wolfcamp formations (Guadalupian age). Mean TDS decreased with further increases in depth. In contrast, the mean salinity of PW was significantly higher within the shallow, younger formations (largest mean TDS in the Artesia Formation); TDS decreased with depth below Guadalupian age formations in the Northwest Shelf. Kriged contour maps of TDS and major ions illustrated spatial variability across the three geo-structural regions as a function of depth. The occurrence of meteoric waters in upper and deeper formations across the three regions was significant, and was attributed to Laramide Orogeny and Basin and Range extension uplifting and tilting effects and recent water flooding. These results quantify PW composition variability, and suggest that upon treatment, PW would support some uses such as onsite reuse and mining.

Air Toxics and Other Volatile Organic Compound Emissions from Unconventional Oil and Gas Development

Unconventional oil and natural gas (UONG) exploration and production have grown rapidly and are expected to increase further in the United States and internationally. Direct measurements of key air pollutant emissions from UONG are limited, especially during drilling and completion (hydraulic fracturing and flowback) of new wells. Knowledge of emission rates (ERs) of air toxics and other air pollutants from these activities is urgently needed to inform public policy. To address this key knowledge gap, we use a tracer ratio method to quantify pad-level, activity-specific [drilling, hydraulic fracturing (“fracking”), flowback, and production] ERs of 46 VOCs in the Denver-Julesburg (D-J, a mixed oil and gas play) and Piceance (primarily natural gas) basins in Colorado. Large differences in ERs of individual VOCs were observed across operation types, across facilities conducting the same operation type, and over time during a single operation. ERs of benzene and most VOCs were highest in both basins during flowback, when injected fracking fluids and produced water flow to the surface. ERs from production are much lower, an important result given the significant difference in the duration of activity (days to weeks for flowback vs decades for production). Fracking ERs of light alkanes and benzene were higher in the Piceance Basin than in the D-J Basin. Findings from this study provide important new information that can be used to evaluate potential health hazards and other air quality impacts of unconventional oil and gas activities in Colorado’s two major oil and gas production basins.

A Fast Numerical Method for the Galvanic Measurement in Hydraulic Fracture Detection

Hydraulic fracturing is critical for unconventional oil and gas production. Recently, galvanic methods, including borehole-to-surface and surface-to-borehole electromagnetic methods, have been applied in hydraulic fracture evaluation. However, conventional computational electromagnetic methods require huge computational cost to simulate the common galvanic fracture model, which consists of a long cased borehole, 3-D thin fractures, and an underground stratified medium. More seriously, modeling both vertical and horizontal energized cased boreholes in layered media is exceptionally difficult. In this article, we present a hybrid numerical mode matching method with stabilized bi-conjugate gradient fast Fourier transform method (NMM-BCGS-FFT) as the forward solver to efficiently model 3-D fractures in the galvanic survey. Both vertical and horizontal energized cased boreholes are modeled in the forward solver. The numerical results show the accuracy and efficiency of the hybrid forward solver. The realistic field galvanic detection model analysis will show the practicability of the forward solver.

Conventional Oil-The Forgotten Part of the Water-Energy Nexus.

The impacts of unconventional oil and gas production via high-volume hydraulic fracturing (HVHF) on water resources, such as water use, groundwater and surface water contamination, and disposal of produced waters, have received a great deal of attention over the past decade. Conventional oil and gas production (e.g., enhanced oil recovery [EOR]), which has been occurring for more than a century in some areas of North America, shares the same environmental concerns, but has received comparatively little attention. Here, we compare the amount of produced water versus saltwater disposal (SWD) and injection for EOR in several prolific hydrocarbon producing regions in the United States and Canada. The total volume of saline and fresh to brackish water injected into depleted oil fields and nonproductive formations is greater than the total volume of produced waters in most regions. The addition of fresh to brackish "makeup" water for EOR may account for the net gain of subsurface water. The total amount of water injected and produced for conventional oil and gas production is greater than that associated with HVHF and unconventional oil and gas production by well over a factor of 10. Reservoir pressure increases from EOR and SWD wells are low compared to injection of fluids for HVHF, however, the longer duration of injections could allow for greater solute transport distances and potential for contamination. Attention should be refocused from the subsurface environmental impacts of HVHF to the oil and gas industry as a whole.

Adsorption and Capillary Condensation-Induced Imbibition in Nanoporous Media.

Multiphase flow phenomena in nanoporous media are encountered in many science and engineering applications. Shales, for example, possessing complex nanopore networks, have considerable importance as source rocks for unconventional oil and gas production and as low-permeability seals for geologic carbon sequestration or nuclear waste disposal. This study presents a theoretical investigation of the processes controlling adsorption, capillary condensation, and imbibition in such nanoporous media, with a particular focus on understanding the effects of fluid-fluid and fluid-pore wall interaction forces in the interconnected nanopore space. Building on a new theoretical framework, we developed a numerical model for the multiphase nanoporous flow and tested it against water vapor uptake measurements conducted on a shale core sample. The model, which is based on the density functional approach, explicitly includes the relevant interaction forces among fluids and solids while allowing for a continuum representation of the porous medium. The experimental data include gravimetrically measured mass changes in an initially dry core sample exposed to varying levels of relative humidity, starting with a low relative humidity (rh = 0.31) followed by a period of a higher relative humidity (rh = 0.81). During this process, water vapor uptake in the dry core is recorded as a function of time. Our model suggests that, under low rh conditions, the flow within the shale sample is controlled by adsorption- and diffusion-type processes. After increasing the rh to 0.81, the uptake of water vapor becomes more significant, and according to our model, this can be explained by capillary condensation followed by immiscible displacement in the core sample. It appears that strong fluid-pore wall attractive forces cause condensation near the inlet, which then induces water imbibition further into sample.

Rapid fingerprinting technology of heavy oil spill by mid-infrared spectroscopy

ABSTRACT With the increase of unconventional oil production and transportation, the detection methods of light crude oil have been challenged. Mid-Infrared spectroscopy can reflect the functional group of the oil related samples, which has strong absorption signals with distinguishable peaks featured as a fast, economy, and robust technique. Nevertheless, the previous study and application of oil relevant samples, such as petroleum chemical industry online monitoring, are mainly based on Near-infrared spectroscopy. Recently, the rapid development of the spectral instrument manufacturing and the data analysis methods provides a more comprehensive technical support for the rapid and accurate identification of marine oil spill by Mid-infrared spectroscopy. In this paper, 10 crude oil samples were selected for infrared spectroscopy detection, and the results were analysed and compared with those of gas chromatography flame ionization detection method. The character information of the IR spectra and GC/FID chromatograms were extracted and classified both by principal component analysis and partial least squares regression. Under the condition of small sample size, the recognition accuracy was up to 100%. The results show that the mid-infrared method combined with chemometrics can be expected to achieve rapid, accurate and economical identification of heavy oil species.

Environmental Justice in Unconventional Oil and Natural Gas Drilling and Production: A Critical Review and Research Agenda.

The drilling phase of oil and natural gas development is a growing area of environmental justice (EJ) research, particularly in the United States. Its emergence complements the longstanding EJ scholarship on later phases of the oil and gas commodity chain, such as pipeline transport, refining, and consumption. The growing scholarly attention to the EJ implications of drilling has been prompted by the surge in development of unconventional oil and gas resources in recent decades. More specifically, the oil and gas industry's adoption of horizontal drilling and hydraulic fracturing (a.k.a., "fracking" or "fracing") as methods for extracting oil and gas from a wider range of geologic formations has simultaneously heightened oil and gas production, brought extractive activities closer to more people, intensified them, and made well pad siting more flexible. Here, we provide a critical review of the novel EJ research questions that are being prompted by these on-the-ground changes in extractive techniques and patterns, propose an interdisciplinary conceptual framework for guiding EJ inquiry in this context, discuss key methodological considerations, and propose a research agenda to motivate future inquiry.