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Results
Hydraulic Fracture Geometry in Highly Laminated Tight Oil Formation: Implication from Large-Scale Rock Experiments and Field Multi-Well Pilot Projects
Yi, Peng (PetroChina RIPED) | Yun, Xu (PetroChina RIPED) | Dingwei, Weng (PetroChina RIPED) | Bo, Huang (Xinjiang Oilfield Engineering Technology Research Institute) | Bin, Xie (Xinjiang Oilfield Engineering Technology Research Institute) | Jiaqi, Li (Xinjiang Oilfield Engineering Technology Research Institute) | Guobin, Jiang (Daqing Oilfield Production Engineering & Research Institute) | Bo, Song (Daqing Oilfield Production Engineering & Research Institute)
Abstract The Lucaogou formation in Junggar basin is the most potential tight oil reservoir in China. However, the disappointing production of a pilot appraisal project with 10 horizontal wells adopting multistage fracturing hold back the further development. The multiple laminated sand-shale formation with horizontal beddings severely affect the fracture height and geometry. This paper provides comprehensive large-scale-block fracturing experiments and field microseismic monitoring data to examine the effect of the highly laminated rock fabric on fracture geometry. Hydraulic fracturing polyaxial tests were conducted using large-scale Lucaogou tight oil outcrops simulating a vertical well and horizontal well respectively. Cross-linked gel and slickwater were used to examine the effect of fluid viscosity on fracture propagation. Fracturing pressure analysis, acoustic emission monitoring, rock splitting and tracing the dyed fluid were combined to investigate the hydraulic fracture geometry and propagation mechanism. Field microseismic monitoring results along with the wellbore trajectory, stress profiles and formation characterization were also analyzed. Large-scale-block fracturing tests show that the treatment pressure in the fracture is increasing steady, which represent the severe fracture containment or high process-zone stress, both are indication of bad stimulation potential. Rock splitting and acoustic emission mapping results proved that fracture initiated and propagated along the horizontal bedding. And the rock heterogeneity and natural fracture play a decisive role in fracture propagation. Field microseismic monitoring results also indicate that the monitoring fracture geometry is much more complicated than predicted. The microseismic mapping shows that fracture propagates downward when the stimulated interval was drilled below the target layer and propagate upward or confined in the pay zone when the interval was drilled above the target layer. Both laboratory and field results suggest that the hydraulic fracture of Luchaogou tight oil reservoir is almost determined both by the landing place in the formation and the natural fractures. Bedding-parallel stimulation would hinder fracture height and more complexity might be observed in a microseismic cloud, but it would probably not beneficial for production. Moreover, when we start flow back and the weight of the overburden is realized, the bedding planes being propped open could lose conductivity because of embedment and proppant pack collapsed. The identification of the target layer in the centimeter-level laminated Luchaogou tight oil formation was challenging and the multiple horizontal beddings severely confined and hinder the fracture propagating vertically, even though larger fluid and proppant volume were injected at higher rate. Well trajectory, natural fracture identification and its direction and layer heterogeneity are the major concerns when stimulated highly laminated formation, which is a typical characteristic of China's tight oil reservoirs.
- North America > United States (1.00)
- Asia > China > Xinjiang Uyghur Autonomous Region (0.24)
- Research Report > New Finding (0.35)
- Research Report > Experimental Study (0.35)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.55)
- Asia > China > Xinjiang Uyghur Autonomous Region > Junggar Basin > Lucaogou Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
- Well Completion > Hydraulic Fracturing > Fracturing materials (fluids, proppant) (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Cluster Spacing Optimization Based on a Multi-Fracture Simultaneous Propagation Model
Lu, Qianli (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University) | Guo, Jianchun (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University) | Zhu, Haiyan (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University) | Zhao, Xing (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University)
Abstract Multi-cluster staged fracturing is an effective method to exploit shale gas. Field observations reported some clusters did not generate fractures. X formation in Sichuan Basin is a 3000m deep shale reservoir. The horizontal stress ratio (Shmax/Shmin) is around 1.4 which is therefore difficult to generate fracture network. How to enable all fractures propagate effectively from each cluster and generate enough stress interference to enable fracture network is of critical concern. This paper established a 2D fracture propagation model based on finite-element method to simulate multi-cluster fracturing. The fracture propagation model couples seepage-stress-damage theories to simulate fracture propagation. The cohesive element is used to simulate the forming of fracture, and the filtration from fracture to matrix is taken into consideration. This model is used to study three fractures propagating simultaneously from three clusters. Different cluster spacing cases were simulated to investigate the fracture geometry and the stress field. When the cluster spacing is 10m, 20m and 30m, the simulation shows that the length of the middle fracture is severely restricted; but for the side fractures, the length is over propagated. When the cluster spacing is 40m and 50m, balanced propagation of all the three fractures is achieved. In 10m, 20m and 30m cases, the stress field shows that in front of the middle fracture, there is a high compressive stress area caused by over propagated side fractures, and this stress could prevent the middle fracture from propagating. So the range of optimized cluster spacing is reduced to greater than 40m. In order to increase the possibility of generating fracture network, the cluster spacing should be small to create high rock frame stress between the fractures. By considering the fracture geometry and stress field, the optimized cluster spacing is 40m cluster. This paper presented a method to optimize the cluster spacing by both considering the fracture geometry and stress field. Cluster spacing optimized by this method could enable the effective propagation of all main fractures and increase the possibility of generating fracture network.
- North America > United States (1.00)
- Asia > China > Sichuan Province (0.25)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.47)
- Geology > Mineral > Silicate > Phyllosilicate (0.47)
- North America > United States > South Dakota > Williston Basin > Bakken Shale Formation (0.99)
- North America > United States > North Dakota > Williston Basin > Bakken Shale Formation (0.99)
- North America > United States > Montana > Williston Basin > Bakken Shale Formation (0.99)
- Asia > China > Sichuan > Sichuan Basin (0.99)