Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Summary The United States National Science Foundation has funded a sustainability-research network focused on natural-gas development in the Rocky Mountain region of the United States. The objective of this specific study is the assessment of the use of existing water wells to monitor the risk of contamination by the migration of fracturing fluids or hydrocarbons to freshwater aquifers. An additional objective of the study is to modify existing risk estimates using the spatial relationships between the existing water wells and producing oil wells. This will allow estimates of single-barrier failure and multiple-barrier failure, resulting in contamination projections for oil and gas wells in areas without surrounding water wells to detect migration, dependent on well-construction type. Since 1970, the Wattenberg Field in Colorado has had a large number of oil and gas wells drilled. These wells are interspaced tightly with agricultural and urban development from the nearby Denver metropolitan area. This provides a setting with numerous water wells that have been drilled within this area of active petroleum development. Data from 17,948 wells drilled were collected and analyzed in Wattenberg Field, allowing wells to be classified by construction type and analyzed for barrier failure and source of aquifer contamination. The assessment confirms that although natural-gas migration occurring in poorly constructed wellbores is infrequent, it can happen, and the migration risk is determined by the well-construction standards. The assessment also confirms that there has been no occurrence of hydraulic-fracturing-fluid contamination of freshwater aquifers through wellbores. The assessment determines both the spatial proximity of oil and gas wells and surface-casing depth to water wells to then determine the utility of water wells to monitor migration in oil wells. Introduction The Wattenberg Field in the Denver-Julesburg Basin, Colorado, began oil and gas production in 1970. The field is the most-active oil and gas field in Colorado and is bordering the highest-population area of the state in the Denver metropolitan area (Figure 1). There are four main producing formations in the field from deepest deposition to shallowest deposition: Muddy-J, Codell, Niobrara, and the Shannon-Sussex Formations.
- North America > United States > Colorado > Weld County (1.00)
- North America > United States > Colorado > Larimer County (1.00)
- North America > United States > Colorado > Denver County (1.00)
- (3 more...)
- Phanerozoic > Mesozoic (0.68)
- Phanerozoic > Paleozoic (0.46)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Geology > Geological Subdiscipline (0.93)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Casing and Cementing > Casing design (1.00)
- Well Completion > Hydraulic Fracturing (1.00)
- (5 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...)
- Information Technology > Artificial Intelligence > Representation & Reasoning > Model-Based Reasoning (0.81)
- Information Technology > Modeling & Simulation (0.68)
Abstract Screenouts of Propped Hydraulic Fracture (PHF) treatments have numerous failure causes, namely, Near-Wellbore Friction, Deviatoric stress, Non-compliant geologic formations, Multiple fractures, Segmented en-echelon fractures, Backstress due to pressure depletion, and, Fracture-tip dilatancy. This paper focuses on the newly-introduced parameter of the Median Ratio (MR) of the Rate Step-down Test (RST) and Near-wellbore (NWB) friction, both of which must be used concurrently as Proppant Admittance (PA) criteria, because screenout causes are not failure diagnosis methods, therefore, not useful in predicting, and/or avoiding screenouts. Each of the PA criteria, while necessary for diagnosis, is not sufficient for accurate prediction of screenout potential, because, when each PA criterion is considered separately it is accurate in 40–45% of the cases, whereas, when both of the PA criteria are used concurrently prediction accuracy increases to over 95%. Therefore, both PA criteria are necessary for accurate Fracture Entry Friction (FEF) analysis, and, prediction of screenout potential. The MR can be determined easily, rapidly, and accurately with the proposed four-equal-step RST procedure. The MR is an empirical function defined as: MR=DP4 / DP1. Concurrent occurrence of: 1) a MR value greater than 0.5, and, 2) a NWB friction value greater that 30 bar (435 psi) is considered: a) an anomaly, b) it is indicative of higher than normal NWB friction, and, c) it is the threshold for PA problems. Both the MR and NWB friction are calculated accurately with enhanced FEF analysis of the RST. The RST has a very short duration, during which, all parameters remain constant: wellbore configuration, perforation configuration, fluid parameters, and fracture dimensions (length, width and height). In addition, pressure loss due to friction is a function of flowrate; hence, progressively smaller pressure reduction steps should be noted as the rate is reduced during the RST. Because all parameters are constant, any deviation from the expected pattern of progressively decreasing pressure loss steps is a strong indication of hindrance to fluid flow, and can only be caused by a restrictive NWB area, and the associated NWB friction. Therefore, the MR and NWB friction are powerful diagnostic criteria of PA, which are useful for the successful design and placement of PHF treatments. The methodology of concurrent usage of the MR and NWB friction, and of the specific four-step RST procedure, has been tested extensively on numerous PHF treatments, in both geologically and geographically diverse conditions. We demonstrate that they provide a high-level of confidence required for pre-mainfrac redesign and modifications to the completion, the treatment procedure, and the treatment schedule, and also, for on-the-fly, real-time decision and control. Utilized wisely, the methodology increases the probability of achieving safe and effective placement of PHF treatments.
- North America > United States > Texas (1.00)
- Europe (1.00)
- Asia > Middle East (0.93)
- North America > United States > Colorado > Denver County (0.28)
- Oceania > Australia > South Australia > Cooper Basin (0.99)
- Oceania > Australia > Queensland > Cooper Basin (0.99)
- North America > United States > Wyoming > DJ (Denver-Julesburg) Basin > Niobrara Formation (0.99)
- (8 more...)
- Well Completion > Hydraulic Fracturing > Fracturing materials (fluids, proppant) (1.00)
- Well Completion > Completion Installation and Operations > Perforating (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Information Technology > Architecture > Real Time Systems (0.68)
- Information Technology > Artificial Intelligence > Representation & Reasoning > Diagnosis (0.34)