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Abstract The unconventional reservoir engineer is required to evaluate increasingly complex data. In additional to the rapid advancement of technology used to complete and stimulate unconventional resources, there has been a proliferation of type curve procedures (i.e. pressure and rate transient analysis), decline techniques, and reservoir modelling strategies in the literature. Specific challenges are the analysis of single and multi-phase flow form hydraulically stimulated horizontal and multi-lateral wells. Although state of the art simulation techniques can be used to model any complex reservoir and well architecture, restrictions on data quality, project schedules, and budgets do not always allow for detailed simulation and analysis. Furthermore, initialization of the numerical model often requires some form of analytical modelling as a precursor to the larger model. However, complex scenarios production analysis or forecasting of horizontal wells, dual and tri-laterals, fracture horizontals as well heterogeneous reservoirs can be simplified by using an proxy model which is accurate (if not exact) with respect to long-term deliverability and resource/reserve estimation. Complex wells and reservoirs can be modelled and analyzed by using a simple homogenous reservoir with effective permeability, skin, and wellbore radius combinations. Examples will demonstrate this procedure would allow for the use of simple analytical software tools in lieu of simulation, or the generation of reliable forecasts in the absence of completion/reservoir data
- Information Technology > Modeling & Simulation (0.68)
- Information Technology > Software (0.48)
Abstract The Changbei basin centred gas reservoir is located in the Palaeozoic clastic sandstone of the Shaanxi formation, Ordos basin, P.R. China. After more than a decade of successful tight gas production history, the development of the field is being expanded to include new target reservoirs. Because of its low intrinsic permeability, hydraulic fracturing stimulations are required to achieve commercial production rates from the target formation. Fracture diagnostics suggests high fluid efficiencies in a normally faulted stress regime. Recent monitoring data of hydraulic fracturing stimulations during an appraisal campaign indicate fracture height growth containment which is not readily predicted by the current numerical simulators. Non-radioactively traced proppant and post-injection temperature logs suggest that fracture height may be controlled by a combination of stress barriers and shale laminations. However, the current numerical simulators tend to have difficulty predicting the termination of height growth without calibration to post-job data. A new hydraulic fracturing code currently under development has been used to simulate the fracture treatments in the target formations. This study briefly describes the input data workflow for the new software and highlights the underlying models the simulations are based upon. The discrepancies between the model results are discussed and possible explanations put forward. The study concludes that the new code is a useful addition to the existing software, and that the thermodynamic module enables genuine comparisons with the temperature logs, which in this case are important for investigating the fracture development. The code also gives promisingly accurate pressure evolutions during the treatment when compared to measurements from a well equipped with a downhole gauge.
- Asia > China > Shaanxi Province (1.00)
- Asia > China > Shanxi Province (0.71)
- Asia > China > Gansu Province (0.71)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.37)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.35)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Passive Seismic Surveying > Microseismic Surveying (0.68)
- Asia > China > Shanxi > Ordos Basin > Changqing Field (0.99)
- Asia > China > Shaanxi > Ordos Basin > Changqing Field (0.99)
- Asia > China > Shaanxi > Ordos Basin > Changbei Field (0.99)
- (3 more...)
Abstract During hydraulic fracture propagation three regions may be identified from the pressure response referred to as: 1) near-well, that extends tens of inches, 2) mid-field, that extends tens of feet and 3) far-field, that extends hundreds of feet from the wellbore. Each region can experience simple, tortuous, and complex fracture behavior creating unique pressure signatures. It has been observed that complex fractures with extended fracture storage can result from hydraulic fracture stimulation in highly deviated and horizontal wells. Complexity is created as a result of induced hydraulic fractures turning and twisting as they exit the wellbore in the near-well region, propagating into the mid-field region, and then re-orienting in the direction of principal stresses in the far-field. This results in anomalously high apparent net pressures as evident by increased ISIP's and rapidly declining pressures that dissipate minutes after shut-in. This paper presents minifrac and post-job pressure matching case studies that identify and describe mid-field fracture complexity (MFC), or extended wellbore pressure storage. The pressure behavior supports complex fracture propagation, high fracturing pressures and pressure fall-off responses typically observed in horizontal shale wells. High apparent fracturing stress gradients are often seen that are much greater than the over-burden stress-gradients. Although suggestive, these high stress gradients are not indicative of horizontal fractures in the far-field. Uncharacteristically high MFC is also not necessarily related to fracture complexity in the far-field. A methodology is presented that identifies the "actual" ISIP which allows for in-situ stress calibration, true net pressure identification, proper minifrac interpretation and an improved fracture treatment design. Rapidly declining pressure during a shut-in as a result of MFC resembles pressure dependent fluid loss and often is misinterpreted as such. However, the pressure response is a result of extended fracture storage and energy dissipation in the mid-field region, which can result in multiple closure signatures. Multiple closure events are indicative of complex fracture network behavior as a result of stress anisotropy and creation of multiple non-planar fractures in the mid-field region. Additionally, hydraulically induced secondary fractures perpendicular to the maximum horizontal stress can provide insight into stress anisotropy. Identifying and incorporating MFC into pressure interpretation analyses will enhance fracture treatment design and post-job pressure matching providing a systematic methodology for designing and analyzing horizontal shale fracture treatments. Information regarding MFC is critical in interpreting fracture treatment pressure responses and optimizing fracture treatment designs in horizontal wells, including well spacing and fracture interference.
- North America > United States > Texas (0.68)
- North America > United States > Pennsylvania (0.47)
- Europe > Denmark > North Sea (0.46)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.48)
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- (45 more...)
A Coupled Model for Fractured Shale Reservoirs with Characteristics of Continuum Media and Fractal Geometry
Wei, Yunsheng (Research Institute of Petroleum Exploration & Development (RIPED), PetroChina) | He, Dongbo (Research Institute of Petroleum Exploration & Development (RIPED), PetroChina) | Wang, Junlei (Research Institute of Petroleum Exploration & Development (RIPED), PetroChina) | Qi, Yadong (Research Institute of Petroleum Exploration & Development (RIPED), PetroChina)
Abstract The principle focus of this work is on proposing a new model to evaluate the production performance of complexly-fractured well in shale reservoirs for conducting rate transient analysis (RTA) and pressure transient analysis (PTA). The model is established on the trilinear-flow idealization presented by Brown et al. (2009) for fractured horizontal well and associated with continuum geometry, fractal characterization and anomalous diffusion. The coupled model could take into account the non-uniform distribution of fracture network within stimulated reservoir volume (SRV) and property heterogeneity among hydraulic fractures in the configuration of multiple fractured horizontal well (MFHW). The second focus is put on developing a novel semi-analytical solution to fill the gap between trilinear-flow model for single-fracture hypothesis and actual MFHW configuration. The new solution could account for the effect of fracture-production interaction and property heterogeneity among fractures. Calculative results show that the type, sequence and duration of flow regimes are determined by fractal characteristics, associated anomalous diffusion, fracture number/spacing, fracture conductivity, etc. Hence, it is possible to observe the feature of long-period linear flow trends in the production performance of fractured well and explain the presentation of new flow regimes which are generally not identified by conventional trilinear-flow model. In addition, approximate solutions for corresponding flow regimes have also been proposed to interpret the production performance using straight forward method. Furthermore, a field example from Sichuan Shale in China is presented to demonstrate the practical application of the new model for interpreting production data analysis of MFHW. The model provides us with new knowledge and insight into understanding production characteristics and allows us to correctly predict well performance in fractured shale reservoirs
- Europe (1.00)
- Asia (1.00)
- North America > United States > Texas (0.28)
- Overview > Innovation (0.88)
- Research Report (0.54)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Sabinas - Rio Grande Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Maverick Basin > Eagle Ford Shale Formation (0.99)
- (2 more...)
Abstract Water influx is an important factor which needs to be quantified during early stages of reservoir development to justify project economics. For a CBM reservoir, it is much more important to quantify a degree of connection & boundary between coal reservoir and aquifer (if any) as its production mechanism is based on efficient dewatering process and any communication of coal seams with adjacent aquifer layercan act as a major barrier for development. However, it is difficult to quantify water influx values early in field life as limited data is available from the reservoir; but pressure transient testing, usually done during exploratory stage can play a pivotal part in reservoir characterization. Currently, solutions exist for analyzing pressure falloff test reponses to quantify water influx in the reservoir in communication with an infinite aquifer. However, there can be cases with limited aquifer extent in which case the use of former solution would lead to wrong estimation of water influx communication. So we propose a new model to account for closed outer boundray of aquifer, and use of this model to estimate both aquifer extent and water influx quantification. Leaky aquifer models more accurately describe bottom water drive reservoirs as most of the time aquifer connection with the reservoir is not perfect (ΔPres. ≠ ΔPaquifer). It is extremely important to quantify connectivity between the aquifer and the main reservoir before going for full field development. The method presented in this paper can provide a much needed solution to quantify the aquifer reservoir connectivity and the aquifer extent for a reservoir with bottom water drive earlier in field life using pressure transient data. We demonstrate the robustness of the proposed method using synthetic example for a homogeneous single well radial reservoir.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.35)
- North America > United States > Wyoming > Powder River Basin (0.99)
- North America > United States > Montana > Powder River Basin (0.99)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Coal seam gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Pressure transient analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)