Monitoring and delineating the spatial distribution of shale fracturing is fundamentally important to shale gas production. Standard monitoring methods, such as time-lapse seismic, cross-well seismic and micro-seismic...Monitoring and delineating the spatial distribution of shale fracturing is fundamentally important to shale gas production. Standard monitoring methods, such as time-lapse seismic, cross-well seismic and micro-seismic methods, are expensive, time- consuming, and do not show the changes in the formation with time. The resistivities of hydraulic fracturing fluid and reservoir rocks were measured. The results suggest that the injection fluid and consequently the injected reservoir are characterized by very low resistivity and high chargeability. This allows using of the controlled-source electromagnetic method （CSEM） to monitor shale gas hydraulic fracturing. Based on the geoelectrical model which was proposed according to the well-log and seismic data in the test area the change rule of the reacted electrical field was studied to account for the change of shale resistivity, and then the normalized residual resistivity method for time lapse processing was given. The time-domain electromagnetic method （TDEM） was used to continuously monitor the shale gas fracturing at the Fulin shale gas field in southern China. A high-power transmitter and multi-channel transient electromagnetic receiver array were adopted. 9 h time series of Ex component of 224 sites which were laid out on the surface and over three fracturing stages of a horizontal well at 2800 m depth was recorded. After data processing and calculation of the normalized resistivity residuals, the changes in the Ex signal were determined and a dynamic 3D image of the change in resistivity was constructed. This allows modeling the spatial distribution of the fracturing fluid. The model results suggest that TDEM is promising for monitoring hydraulic fracturing of shale.展开更多
The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore...The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.展开更多
Burial depth,thickness,total organic carbon(TOC)content,brittleness and fracture development of shale reservoirs are the main geologic indexes in the evaluation of sweet spots in shale gas plays.Taking the 2nd interva...Burial depth,thickness,total organic carbon(TOC)content,brittleness and fracture development of shale reservoirs are the main geologic indexes in the evaluation of sweet spots in shale gas plays.Taking the 2nd interval of Da'anzhai shale of the Lower Jurassic as the study object,a set of techniques in seismic prediction of sweet spots were developed based on special processing of seismic data and comprehensive analysis of various data based on these geologic indexes.First,logging and seismic responses of high quality shales were found out through fine calibration of shale reservoir location with seismogram,which was combined with seismic facies analysis to define the macroscopic distribution of the shale.Then,seismic impedance inversion and GR inversion were used to identify shale from limestone and sandstone.Based on statistical analysis of sensitive parameters such as TOC,the uranium log inversion technique was used to quantitatively predict TOC of a shale reservoir and the thickness of a high quality shale reservoir.After that,fracture prediction technique was employed to predict play fairways.Finally,the pre-stack joint P-wave and S-wave impedance inversion technique was adopted to identify shales with high brittleness suitable for hydraulic fracturing.These seismic prediction techniques have been applied in sorting out sweet spots in the 2nd interval of the Da'anzhai shale play of the Yuanba area,and the results provided a sound basis for the optimization of horizontal well placement and hydraulic fracturing.展开更多
基金supported by NSFC(Grant No.U1562109 and 41774082)the National Major Research Plan(Grant No.2016YFC0601100and 2016ZX05004)the Project of Scientific Research and Technological Development,CNPC(Grant No.2017D-5006-16)
文摘Monitoring and delineating the spatial distribution of shale fracturing is fundamentally important to shale gas production. Standard monitoring methods, such as time-lapse seismic, cross-well seismic and micro-seismic methods, are expensive, time- consuming, and do not show the changes in the formation with time. The resistivities of hydraulic fracturing fluid and reservoir rocks were measured. The results suggest that the injection fluid and consequently the injected reservoir are characterized by very low resistivity and high chargeability. This allows using of the controlled-source electromagnetic method （CSEM） to monitor shale gas hydraulic fracturing. Based on the geoelectrical model which was proposed according to the well-log and seismic data in the test area the change rule of the reacted electrical field was studied to account for the change of shale resistivity, and then the normalized residual resistivity method for time lapse processing was given. The time-domain electromagnetic method （TDEM） was used to continuously monitor the shale gas fracturing at the Fulin shale gas field in southern China. A high-power transmitter and multi-channel transient electromagnetic receiver array were adopted. 9 h time series of Ex component of 224 sites which were laid out on the surface and over three fracturing stages of a horizontal well at 2800 m depth was recorded. After data processing and calculation of the normalized resistivity residuals, the changes in the Ex signal were determined and a dynamic 3D image of the change in resistivity was constructed. This allows modeling the spatial distribution of the fracturing fluid. The model results suggest that TDEM is promising for monitoring hydraulic fracturing of shale.
基金Major Project of National Science and Technology(No.2011ZX05004-005)Major Project of Exploration of PetroChina“Hydrocarbon Evaluation of Leshan-Longnüsi Palaeohigh in Sichuan Basin and Research on Exploration Support Technologies”(No.2012ZD01-03-01)。
文摘The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.
基金Scientific research project of China Petroleum&Chemical Corporation(No.P13129).
文摘Burial depth,thickness,total organic carbon(TOC)content,brittleness and fracture development of shale reservoirs are the main geologic indexes in the evaluation of sweet spots in shale gas plays.Taking the 2nd interval of Da'anzhai shale of the Lower Jurassic as the study object,a set of techniques in seismic prediction of sweet spots were developed based on special processing of seismic data and comprehensive analysis of various data based on these geologic indexes.First,logging and seismic responses of high quality shales were found out through fine calibration of shale reservoir location with seismogram,which was combined with seismic facies analysis to define the macroscopic distribution of the shale.Then,seismic impedance inversion and GR inversion were used to identify shale from limestone and sandstone.Based on statistical analysis of sensitive parameters such as TOC,the uranium log inversion technique was used to quantitatively predict TOC of a shale reservoir and the thickness of a high quality shale reservoir.After that,fracture prediction technique was employed to predict play fairways.Finally,the pre-stack joint P-wave and S-wave impedance inversion technique was adopted to identify shales with high brittleness suitable for hydraulic fracturing.These seismic prediction techniques have been applied in sorting out sweet spots in the 2nd interval of the Da'anzhai shale play of the Yuanba area,and the results provided a sound basis for the optimization of horizontal well placement and hydraulic fracturing.
