Drilling results suggest that the thickness of natural gas hydrates(NGHs)in the Shenhu Area,South China Sea(SCS)are spatially heterogenous,making it difficult to accurately assess the NGHs resources in this area.In th...Drilling results suggest that the thickness of natural gas hydrates(NGHs)in the Shenhu Area,South China Sea(SCS)are spatially heterogenous,making it difficult to accurately assess the NGHs resources in this area.In the case that free gas exists beneath hydrate deposits,the frequency of the hydrate deposits will be noticeably attenuated,with the attenuation degree mainly affected by pore development and free gas content.Therefore,the frequency can be used as an important attribute to identify hydrate reservoirs.Based on the time-frequency characteristics of deposits,this study predicted the spatial distribution of hydrates in this area using the frequency division inversion method as follows.Firstly,the support vector machine(SVM)method was employed to study the amplitude versus frequency(AVF)response based on seismic and well logging data.Afterward,the AVF response was introduced as independent information to establish the nonlinear relationship between logging data and seismic waveform.Then,the full frequency band information of the seismic data was fully utilized to obtain the results of frequency division inversion.The inversion results can effectively broaden the frequency band,reflect the NGHs distribution,and reveal the NGHs reservoirs of two types,namely the fluid migration pathway type and the in situ self-generation self-storage diffusion type.Moreover,the inversion results well coincide with the drilling results.Therefore,it is feasible to use the frequency division inversion to predict the spatial distribution of heterogeneous NGHs reservoirs,which facilitates the optimization of favorable drilling targets and is crucial to the resource potential assessment of NGHs.展开更多
The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial...The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.展开更多
基金supported by the National Research and Development Fund entitled“High Precision Characterization Technology of Natural Gas Hydrates Reservoirs”(2017YFC0307406)the projects entitled“Integrated Observation Data Integration and Application Service of Natural Resource Elements”(DD20208067)+2 种基金“Comprehensive geological survey of coastal zone and reef in the Northern Jiaodong”(ZD20220604)initiated by the China Geological Surveythe project entitled“Study on Hydrocarbon Accumulation Failure and Fluid Evolution Reduction of the Permian Reservoir in the Laoshan Uplift,South Yellow Sea”(42076220)“Temporal and Spatial Distribution Characteristics and Provenance of Two Stages Paleo-deltas on the Outer Shelf in the North of the East China Sea since Late Pleistocene”(41706069)organized by the National Natural Science Foundation of China。
文摘Drilling results suggest that the thickness of natural gas hydrates(NGHs)in the Shenhu Area,South China Sea(SCS)are spatially heterogenous,making it difficult to accurately assess the NGHs resources in this area.In the case that free gas exists beneath hydrate deposits,the frequency of the hydrate deposits will be noticeably attenuated,with the attenuation degree mainly affected by pore development and free gas content.Therefore,the frequency can be used as an important attribute to identify hydrate reservoirs.Based on the time-frequency characteristics of deposits,this study predicted the spatial distribution of hydrates in this area using the frequency division inversion method as follows.Firstly,the support vector machine(SVM)method was employed to study the amplitude versus frequency(AVF)response based on seismic and well logging data.Afterward,the AVF response was introduced as independent information to establish the nonlinear relationship between logging data and seismic waveform.Then,the full frequency band information of the seismic data was fully utilized to obtain the results of frequency division inversion.The inversion results can effectively broaden the frequency band,reflect the NGHs distribution,and reveal the NGHs reservoirs of two types,namely the fluid migration pathway type and the in situ self-generation self-storage diffusion type.Moreover,the inversion results well coincide with the drilling results.Therefore,it is feasible to use the frequency division inversion to predict the spatial distribution of heterogeneous NGHs reservoirs,which facilitates the optimization of favorable drilling targets and is crucial to the resource potential assessment of NGHs.
基金supported by the National Major Science and Technology Project“Hydrocarbon generation and expulsion mechanism of marine source strata and evaluation technology”(No.:2017ZX05005-001-003)the Science&Technology Project of Sinopec Exploration Company“Evaluation on hydrocarbon generation potential in Mao 1 Member,Fuling area”(No.:35450003-17-ZC0607-0032).
文摘The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.
