Results
Development of unconventional plays requires an early election of horizontal well targeting and spacing. As operators fine-tune development plans, changes to that initial framework can take years to implement due to long lead times for land, permitting, and planning. However, hydraulic fracturing design remains a more flexible design element, representing a powerful force for optimization. With a combination of accessible physics-based modeling and data analysis, engineers can see through the noise of multi-variate systems to create high-confidence integrated well spacing and completion designs for frontier and mature field development and for campaigns that have been drilled but not yet stimulated. This approach mixes long-standing reservoir engineering practices with developing ideas about how to represent the hydraulic fracturing process and response.
- North America > United States > Wyoming (0.21)
- North America > United States > Nebraska (0.21)
- North America > United States > Kansas (0.21)
- North America > United States > Colorado (0.21)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- North America > United States > Nebraska > Niobrara Formation (0.99)
- (5 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics (1.00)
- Management > Asset and Portfolio Management > Field development optimization and planning (0.97)
Well Interference and Fracture Geometry Investigation Using Production and Low-Frequency Distributed Acoustic Sensing Data in an Unconventional Reservoir
Ning, Yanrui (Colorado School of Mines (Corresponding author)) | Jin, Ge (Colorado School of Mines) | Zhu, Xiaoyu (Colorado School of Mines) | Tura, Ali (Colorado School of Mines)
Summary Well interference directly impacts well spacing optimization and well economics, thus it has received significant attention. Observed in many unconventional reservoirs, well interference is mainly attributed to connection of hydraulic fractures. Few studies have compared the hydraulic fracture connection during stimulation with that during the production period. This study connects these two aspects by leveraging the low-frequency distributed acoustic sensing (LF-DAS) signals acquired during the stimulation and the daily production data of 23 horizontal wells in the Denver-Julesburg (DJ) Basin. Strong cross-formation communication between Niobrara and Codell has been identified from both LF-DAS and production data. Interwell fracture connection could divert up to 80% of a shut-in well's production to the offset well in the adjacent formation, revealing that well interference can be evaluated through random shut-ins of wells during production. Further, fracture connection in LF-DAS data is observed between Codell wells but rarely between Niobrara wells. Given the average Codell well spacing of 1,270 ft and Niobrara well spacing of 650 ft, we observe that the half-length of the stimulated hydraulic fractures in Codell wells is significantly longer than that of Niobrara wells. This study also confirms that stronger well interference during production correlates with strong fracture connection identified from LF-DAS. Introduction Multistage hydraulic fracturing stimulation is a standard technique to recover hydrocarbon from unconventional reservoirs. Appropriate well spacing is an important contributing factor to extract more hydrocarbon in place with minimal cost. From 2009 until recently, when targeting the Niobrara and Codell formations in Denver-Julesburg (DJ) Basin, well densities have increased from 1 horizontal well per section to 11-15 horizontal wells per section (Milne and Cumella 2014; Anderson et al. 2015; Ning et al. 2017).
- North America > United States > Wyoming (1.00)
- North America > United States > Colorado (1.00)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Vaca Muerta Shale Formation (0.99)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Loma Campana Field > Vaca Muerta Shale Formation (0.99)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Loma Campana Field > Lower Agrio Formation (0.99)
- (26 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
Application of Fracture Injection Test, Rate Transient Analysis, and Pearson Correlation in Niobrara and Codell Formations to Evaluate Reservoir Performance in a Northern DJ Basin
Mindygaliyeva, B. (Colorado School of Mines) | Bekbossinov, N. (Colorado School of Mines) | Kazemi, H. (Colorado School of Mines)
ABSTRACT: This paper presents an assessment of well drilling strategy and the associated hydraulic fracture stimulation for a field in the Northern DJ Basin, Colorado. The paper is rich in data related to well orientation, completion, and production over a ten-year period from an unconventional field. Shale formations have very low permeabilities; however, multistage hydraulic fracturing stimulates the rock matrix by inducing micro- and macro-cracks; thus, improving formation drainage. Subsequently, rate transient analysis (RTA) of production data determines the quality of well stimulation. RTA emanates from single-phase linear-flow theory using rate-normalized-pressure versus (Equation) of the production data; however, RTA also extends to multiphase flow. RTA yields the effective formation permeability (EFP) and, occasionally, hydraulic fracture conductivity (HFC). Additionally, we used an iterative Perkins-Kern-Nordgren (PKN) model to interpret diagnostic fracture injection tests (DFIT) for the unstimulated formation permeability. Finally, we used 21 variables to generate a ‘correlation map’ of various reservoir performance measures: well s pacing, lateral length, number of perforations, total stimulation fluid injected, amount of sand placed, sand mesh size, quantity of p roduced oil, gas, and water. The variables that yielded the strongest positive correlation coefficients were well spacing, produced oil and gas volumes, 20/40 sand, acid additives, EFP, and HFC. 1. INTRODUCTION The Shale formations are denoted as ‘tight’ reservoir plays with low, nano-Darcy, matrix permeabilities where pore-size distribution is in the nanometer higher frequencies (Luo, 2018). Because of low matrix permeability, the maturation of the organic matter takes place in the source rock and the resultant distribution of hydrocarbon components also remains within the source rock with little outward migration. Formations with such characteristics are designated ‘unconventional reservoir’. There is a continued demand for hydrocarbon production due to the global energy demand and population growth. Fortunately, innovations in the technological sector of the oil and gas industry has provided effective means of oil and gas recovery from such tight formations (Kazemi et al., 2015). Contribution of unconventional reservoirs is significant in maintaining the balance in the energy market (Cui, 2015).
- North America > United States > Wyoming (1.00)
- North America > United States > Colorado (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.94)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- North America > United States > Texas > Permian Basin > Delaware Basin (0.99)
- (11 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- (2 more...)
Abstract Well interference directly impacts well spacing optimization and well economics, thus it has received significant attention. Observed in many unconventional reservoirs, well interference is mainly attributed to connection of hydraulic fractures. Few studies have compared the hydraulic fracture connection during stimulation with that during the production period. This study connects these two aspects by leveraging the low-frequency Distributed Acoustic Sensing (LF-DAS) signals acquired during the stimulation and the daily production data of 23 horizontal wells in the Denver-Julesburg (DJ) Basin. Strong cross-formation communication between Niobrara and Codell has been identified from both LF-DAS and production data. Interwell fracture connection could divert up to 80% of a shut-in well's production to the offset well in the adjacent formation, revealing that well interference can be evaluated through random shut-ins of wells during production. Further, fracture connection in LF-DAS data is observed between Codell wells but rarely between Niobrara wells. Given the average Codell well spacing of 1270 ft and Niobrara well spacing of 650 ft, we observe that the half-length of the stimulated hydraulic fractures in Codell wells is significantly longer than that of Niobrara wells. This study also confirms that stronger well interference during production correlates with strong fracture connection identified from LF-DAS. Introduction Multistage hydraulic fracturing stimulation is a standard technique to recover hydrocarbon from unconventional reservoirs. Appropriate well spacing is an important contributing factor to extract more hydrocarbon in place with minimal cost. From 2009 until recently, when targeting the Niobrara and Codell formations in DJ Basin, well densities have increased from one horizontal well per section to 11-15 horizontal wells per section (Milne and Cumella, 2014; Anderson et al., 2015; Ning, 2017). As more wells are drilled, wells tend to communicate with their neighbors and well interference has been observed in many unconventional plays such as Haynesville shale, Marcellus shale, and Eagle Ford (Khodabakhshnejad, 2019; Gupta et al. 2020; Raterman et al. 2020). In the Eagle Ford, a well spacing of 400 – 800 ft is likely to facilitate communication between offsets (Raterman et al. 2019). It is essential to understand well interference because it directly affects well spacing optimization and thus impacts the economic development of unconventional reservoirs (Portis et al. 2013; Yaich et al. 2014; Lindner and Bello 2015; Rimedio et al. 2015).
- North America > United States > Texas (1.00)
- North America > United States > Colorado (1.00)
- Geology > Petroleum Play Type > Unconventional Play > Shale Play > Shale Gas Play (0.68)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.45)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Vaca Muerta Shale Formation (0.99)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Loma Campana Field > Vaca Muerta Shale Formation (0.99)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Loma Campana Field > Lower Agrio Formation (0.99)
- (25 more...)
- Well Completion > Hydraulic Fracturing > Multistage fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Management > Asset and Portfolio Management > Field development optimization and planning (1.00)
Dimensionless Section-Level Cumulative Oil Vs. Pumped Fluid Normalization Plot in Unconventional Development
Rosenhagen, Nicolas M. (Colorado School of Mines) | Nash, Steven D. (Anadarko Petroleum Corporation) | Dobbs, Walter C. (Anadarko Petroleum Corporation) | Tanner, Kevin V. (Anadarko Petroleum Corporation)
Abstract The volume of stimulation fluid injected during hydraulic fracturing is a key performance driver in the horizontal development of the Niobrara formation in the Denver-Julesburg (DJ) Basin, Colorado. Oil production per well generally increases with stimulation fluid volume. Often, operators normalize both production and fluid volume based on stimulated lateral length and investigate relationships using "per-ft" variables. However, data from well-based approaches commonly display such wide distributions that no useful relationships can be inferred. To improve data correlations, multivariate analysis normalizes for parameters such as thermal maturity, depth, depletion, proppant intensity, drawdown, geology and completion design. Although advancements in computing power have decreased cycle times for multivariate analysis, preparing a clean dataset for thousands of wells remains challenging. A proposed analytical method using publicly available data allows interpreters to see through the noise and find informative correlations. Using a data set of over 5000 wells, we aggregate cumulative oil production and stimulation fluid volumes to a per-section basis then normalize by hydrocarbon pore volume (HCPV) per section. Dimensionless section-level Cumulative Oil versus Stimulation Fluid Plots ("Normalization" or "N-Plot") present data distributions sufficiently well-defined to provide an interpretation and design basis of well spacing and stimulation fluid volumes for multi-well development. When coupled with geologic characterization, the trends guide further refinement of development optimization and well performance predictions. Two example applications using the N-Plot are introduced. The first involves construction of predictive production models and associated evaluation of alternative development scenarios with different combinations of well spacing and completion fluid intensity. The second involves "just-in-time" modification of fluid intensity for drilled but uncompleted wells (DUC's) to optimize cost-forward project economics in an evolving commodity price environment.
- North America > United States > Wyoming (1.00)
- North America > United States > Colorado (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.47)
- Geology > Geological Subdiscipline > Stratigraphy (0.46)
- Geology > Geological Subdiscipline > Geomechanics (0.46)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > Laramie Basin > Niobrara Formation (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- (48 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Management > Energy Economics > Unconventional resource economics (1.00)
- Reservoir Description and Dynamics > Fluid Characterization > Fluid modeling, equations of state (0.94)
- (2 more...)
Abstract In some basins, large scale development of unconventional stacked-target plays requires early election of well targeting and spacing. Changes to the initial well construction framework can take years to implement due to lead times for land, permitting, and corporate planning. Over time, as operators wish to fine tune their development plans, completion design flexibility represents a powerful force for optimization. Hydraulic fracturing treatment plans may be adjusted and customized close to the time of investment. With a practical approach that takes advantage of physics-based modeling and data analysis, we demonstrate how to create a high-confidence, integrated well spacing and completion design strategy for both frontier and mature field development. The Dynamic Stimulated Reservoir Volume (DSRV) workflow forms the backbone of the physics-based approach, constraining simulations against treatment, flow-back, production, and pressure-buildup (PBU) data. Depending on the amount of input data available and mechanisms investigated, one can invoke various levels of rigor in coupling geomechanics and fluid flow – ranging from proxies to full iterative coupling. To answer spacing and completions questions in the Denver Basin, also known as the Denver-Julesburg (DJ) Basin, we extend this modeling workflow to multi-well, multi-target, and multi-variate space. With proper calibration, we are able generate production performance predictions across the field for a range of subsurface, well spacing, and completion scenarios. Results allow us to co-optimize well spacing and completion size for this multi-layer column. Insights about the impacts of geology and reservoir conditions highlight the potential for design customization across the play. Results are further validated against actual data using an elegant multi-well surveillance technique that better illuminates design space. Several elements of subsurface characterization potentially impact the interactions among design variables. In particular, reservoir fluid property variations create important effects during injection and production. Also, both data analysis and modeling support a key relationship involving well spacing and the efficient creation of stimulated reservoir volumes. This relationship provides a lever that can be utilized to improve value based on corporate needs and commodity price. We introduce these observations to be further tested in the field and models.
- North America > United States > Wyoming (1.00)
- North America > United States > Colorado (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.47)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > Laramie Basin > Niobrara Formation (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- (22 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- (5 more...)
Abstract This paper presents construction and validation of a reservoir model for the Niobrara and Codell Formations in Wattenberg Field of the Denver-Julesburg Basin. Characterization of Niobrara-Codell system is challenging because of the geologic complexity resulting from the presence of numerous faults. Because of extensive reservoir stimulation via multi-stage hydraulic fracturing, a dual-porosity model was adopted to represent the various reservoir complexities using data from geology, geophysics, petrophysics, well completion and production. After successful history matching two-and-half years of reservoir performance, the localized presence of high intensity macrofractures and resulting evolution of gas saturation was correlated with the time-lapse seismic and microseismic interpretations. The agreement between the evolved free gas saturation in the fracture system and the seismic anomalies and microseismic events pointed to the viability of the dual-porosity modeling as a tool for forecasting and future reservoir development, such as re-stimulation, infill drilling, and enhanced oil recovery strategies.
- North America > United States > Colorado > Weld County (0.37)
- North America > United States > Colorado > Denver County (0.37)
- North America > United States > Colorado > Larimer County (0.27)
- (3 more...)
- Geology > Rock Type > Sedimentary Rock (0.70)
- Geology > Structural Geology > Fault (0.69)
- Geology > Geological Subdiscipline > Geomechanics (0.46)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > Laramie Basin > Niobrara Formation (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- (13 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
Abstract Unconventional completions in North America have seen a paradigm shift in volumes of proppant pumped since 2014. There is a clear noticeable trend in both oil prices and proppant volumes – thanks to low product and service costs that accompanied the oil price crash in early 2015. As the industry continues to recover, operators are reevaluating completion designs to understand if these proppant volumes are beyond what is optimal. This paper analyzes trends in completion sizes and types across all major unconventional oil and gas plays in the US since 2011 and tracks their impact on well productivity. Completion and production data since 2011 from more than 70,000 horizontal wells in seven major basins (Gulf Coast, Permian, Appalachian, Anadarko, Haynesville, Williston and Denver Julesburg basins) and 11 major oil/gas producing formations were analyzed to examine developments in proppant and fluid volumes. Average concentration of proppant per gallon of fluid pumped was used to understand transitional trends in fracturing fluid types with time. Production performance indicators such as First month, Best 3 or Best 12 months of oil and gas production were mapped against completion volumes to evaluate if there are added economic advantages to pumping larger designs. In general, all major basins have seen progressive improvements in average well performance since 2011, with the Permian Basin showing the highest improvement, increasing from an average first-six-months oil production of 25,000 bbl in 2011 to 75,000 bbl in 2017. The Gulf Coast basin, where the Eagle Ford formation is located, has seen a 6-fold increase in proppant volumes pumped per foot of lateral since 2011 while the Permian and Appalachian basins hit peak proppant volumes in 2015 and 2016 respectively. In Permian and Eagleford wells, higher proppant volumes in general have resulted in better production up to a certain concentration. In Williston and Denver basins, most operators are moving away from gelled fluids, and reduced average proppant concentration per fluid volume pumped shows inclination toward hybrid or slickwater designs. While some of these observations are tied to reservoir quality, proppant volumes have begun to peak as operators have either reached an optimal point or are in the process of reducing volumes. Demand for proppant is expected to nearly double by 2020. As oil prices continue to recover, well AFEs continue to increase, despite multiple efforts to improve capital efficiency. The need for enhanced fracture conductivity and extended half-lengths on EURs are been discussed by combining actual observed production data and sensitivities using calibrated production models. The industry is moving toward large-volume slickwater fracturing operations using smaller proppants, but he operating landscape is expected to see a correction when such designs become less economical.
- North America > United States > Texas (1.00)
- North America > United States > Oklahoma (1.00)
- North America > United States > North Dakota (1.00)
- (4 more...)
- Phanerozoic > Paleozoic > Permian (1.00)
- Phanerozoic > Paleozoic > Devonian (0.93)
- Phanerozoic > Paleozoic > Carboniferous > Mississippian (0.69)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Petroleum Play Type > Unconventional Play > Shale Play (0.94)
- Geology > Structural Geology > Tectonics (0.69)
- (2 more...)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.46)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- North America > United States > Wyoming > Laramie Basin > Niobrara Formation (0.99)
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- (97 more...)
Abstract Accelerating the learning curve in the development of the Vaca Muerta utilizing lessons learned in North American unconventional resource plays is the focus of this paper. Reducing completion costs while maintaining high productivity has become a key objective in the current low-price environment. Completion diagnostics have been demonstrated to optimize stimulation and completion parameters that have shaped successful field developments. The paper reviews stimulation diagnostic data from wells completed in the Tuscaloosa Marine Shale, Eagle Ford, Wolfcamp and Niobrara shale formations. Case histories are presented in which proppant and fluid tracers were successfully employed in completion optimization processes. In the examples presented, diagnostic results were used to assess the stimulation of high productivity intervals within a target zone, evaluate various completion methods, and optimize stage and cluster spacing. The diagnostic data were compared with post-frac production rates in an effort to correlate completion changes with well performance. Results presented compare first, engineered perforations versus conventional geometrically spaced perforations to drive up effectiveness in cluster stimulation. Second, new chemistries, such as nanosurfactant, versus conventional chemistries to cut either completion cost or prove their profitability. Third, employing an effective choke management strategy to improve well productivity. Last, as in any stacked pay, determining fracture height growth in order to optimize well density, well spacing, field development and ultimately the recovery of the natural resources. Completion effectiveness is shown to be improved by landing laterals in high productivity target intervals, increasing proppant coverage across the lateral by utilizing the most effective completion methods, optimizing cluster spacing and decreasing the number of stages to reduce completion costs while achieving comparable production rates. Cluster treatment efficiency (CTE), in particular, has become a critical metric when optimizing hydraulic fracturing treatment designs based on current and future well densities. It can be used to rationalize well performance as well as to identify possible candidates for a refrac program. Using completion diagnostics, successful completion techniques were identified that led to production enhancements and cost reductions in prolific plays such as the Tuscaloosa Marine Shale, Eagle Ford, Wolfcamp and Niobrara.
- North America > United States > Wyoming (1.00)
- North America > United States > Texas (1.00)
- North America > United States > Colorado (1.00)
- North America > United States > Nebraska (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Petroleum Play Type > Unconventional Play (1.00)
- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Vaca Muerta Shale Formation (0.99)
- North America > United States > Wyoming > Uinta Basin (0.99)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- (30 more...)
- Well Completion > Hydraulic Fracturing > Fracturing materials (fluids, proppant) (1.00)
- Well Completion > Completion Installation and Operations > Perforating (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs (1.00)
- (5 more...)
The Niobrara Shale in the United States has ramped up into a hot play that could soon bring an explosion of horizontal drilling in Colorado and Wyoming. The combination of horizontal drilling and multistage hydraulic fracturing is transforming the Niobrara from a target that has been drilled vertically and primarily for gas for nearly 100 years into a liquids-rich play that is capturing considerable attention. Speaking at the 2011 SPE Annual Technical Conference and Exhibition in Denver, John Ford, general manager of Colorado’s Wattenberg field at Anadarko, described the growing Niobrara activity as “really the next big thing.” That optimism was understandable. In November, Anadarko announced that its leases at Wattenberg may hold more than a billion barrels of recoverable oil and natural gas. The statement noted company drilling success in 11 recent wells at the field, including the Dolph 27-1HZ horizontal well that showed initial production of more than 1,100 B/D of oil and 2.4 MMcf/D of natural gas. These latest wells have given the company confidence that it can drill between 1,200 and 2,700 wells in northeast Colorado, with approximately 160 wells planned for this year. Based on results so far, the company expects ultimate recovery of between 500 million and 1.5 billion bbl of oil, natural gas liquids, and natural gas on an equivalent basis. Anadarko is not alone. Chesapeake Energy, Noble, Encana, and EOG Resources are among the largest acreage holders and the most active drillers of many companies—including numerous small independents—probing the Niobrara. Majors such as Shell and Marathon Oil have significant acreage. There are more than 50 operators in or near the Wattenberg field alone. Situated north/northeast of the Denver area, Wattenberg is the largest producing field in the Denver-Julesburg (D-J) Basin and one of the largest onshore oil and gas fields in the US. Reservoir Rock and Producing Regions Although the Niobrara is usually referred to as a shale, its reservoir rock consists primarily of limestone or chalk intervals, said Steve Sonnenberg, professor of petroleum geology at Colorado School of Mines in a recent edition of the AAPG Explorer (published by the American Association of Petroleum Geologists). “The formation demonstrates facies changes that range from limestone and chalk in the eastern end to calcareous shale in the middle and eventually transitioning to sandstone farther west,” said Sonnenberg, a past president of AAPG. “Depth and thickness are highly variable.”
- North America > United States > Colorado > Weld County (0.71)
- North America > United States > Colorado > Larimer County (0.46)
- North America > United States > Colorado > Denver County (0.46)
- (3 more...)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.66)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.45)
- North America > United States > Wyoming > Sand Wash Basin (0.99)
- North America > United States > Wyoming > Powder River Basin (0.99)
- North America > United States > Wyoming > Niobrara Formation (0.99)
- (31 more...)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics (1.00)