地应力技术研究裂缝的渗透性.ppt

1、Fracture Permeability,From a Joint to a Fault,Faulting is key to increasing the permeability of a formation,The Critically Stressed Fracture Concept,Pre-existing fractures and faults are very important in controlling permeability in many reservoirs Mode II and III fractures that are optimally orient

2、ed to todays stress field to be open in shear (critically stressed fractures) provide the permeable pathways for fluid flow. Mode I fractures (opening mode joints) are unlikely to be as important in controlling flow as mode II and III shear fractures (faults) in many reservoirs unless effective stre

3、ss is extremely low (i.e., pore pressure is close to lithostatic). Wellbore image logging is needed to provide detailed information about fractures at depth. The 3-D stress state is an essential component of the analysis of critically stressed fractures and faults. Does not predict fracture orientat

4、ions and densities,3-D Mohr Circle,Conventional Thinking (very rare in nature),Fracture Permeability Mechanisms,Map view of fractures,Hydraulically Conductive, Critically Stressed (Repeated Fault Slip Is Preserving Permeability),Hydraulically Non-Conductive; Stable Faults,Mohr-Coulomb Criterion,Rela

5、tionship Between Critically-Stressed Fractures and Fluid Flow,Permeable Fracture,Impermeable Fracture,Correlation Between Natural Fractures and Reservoir Fluid Flow,Fracture Discrimination Based on Thermal Perturbations in the Borehole,Business Impact Permeability Enhancement,Optimizing well traject

6、ories to intersect permeable fracture sets can increase production rates by an order of magnitude. With knowledge of the distribution of critically stressed fracture sets, operators can optimize hydraulic communication with the reservoir, AND can successfully implement enhanced recovery and redrilli

7、ng strategies. Understanding critically stressed fracture distribution in reservoirs can help to avoid costly drilling problems associated with casing shear.,Permeability of Fractured Reservoirs - Workflow,Natural Fracture Characterization,Case Study - Geothermal,Dixie Valley Geothermal Production,C

8、onceptual Model,Shmin Orientations from Image Analysis,Stress Orientation and Magnitudes,Conductive vs. Non-Conductive Fractures,Central Nevada Permeability Enhancement,Breakouts rotate at active faults due to localized stress drop,A distinct correlation between critically stressed fractures and hyd

9、raulic conductivity,ACTIVE FAULT,Business Impact Central Nevada,The operator of this large Geothermal field can now locate and design production and injection wells to optimize hydraulic communication with the reservoir. Knowledge of which fracture and faults provide conduits for flow has enabled th

10、e operator to design enhanced recovery and redrilling strategies (massive hydrofrac stimulation operations, side tracks). It is now possible to identify locations and depths where excessive fluid losses might present a drilling problem.,Critically Stressed Fractures can Occur in All Stress Regimes,C

11、omposite of Fractures From Three Different Stress States,Oil-filled breccia Monetrey Shale,Seismic activity provides direct evidence of critically stressed fractures and faults,Hydrocarbon Saturated Breccia Zones From Pt. Arguello Area,oil staining,DSTs in Well A,High permeability obtained from dril

12、l stem tests in Well A suggest a correlation of a clustered fracture population that is well oriented for slip in the Pt. Arguello strike slip faulting regime,Business Impact Santa Maria Basin California,The operator of these offshore and onshore wells markedly improved their understanding of fractu

13、re permeability in the Santa Maria Basin. Careful delineation of fracture sets within specific lithologies of the Monetrey sequence provided an important tool to distinguish zones where brittle fracturing of the cherts and dolostones dominates the more ductile mechanical behavior of shales. Fluid mi

14、gration pathways in this basin are limited to the set of optimally oriented, critically stressed fractures in the more brittle dolostones and cherts. This distinction, based on the mechanical behavior of these fractures sets, enabled the operators to precisely select the depth for well placement.,No

15、rth America Production Enhancement,SHmax orientation is structurally controlled - need stress orientation measurements at the well location rather than using regional stress data,Production is enhanced when wells are drilled 70 to the Northwest,Business Impact North America,Since the application of

16、GMIs technologies the operators report remarkable success. The overall well placement strategy has had a “100% economic success rate, production in this structure has performed better than you might have anticipated”. Production in comparable horizontal wells has increased from 800 BOPD to 5000 BOPD

17、 Knowledge of the stress field has allowed drilling of highly successful horizontal wells in several fields utilizing the critically-stressed fault hypothesis of GMI. Knowledge of the full stress tensor also enabled the operators to select well trajectories and mud weights that avoided wellbore stability problems and optimized hydraulic fracturing operations.,Fracture Permeability - Final Remarks,A strong correlation exists between critically stressed faults and hydraulic conductivity in highly fractured crystalline rock. This correlation can be used to help pred