Seismic Rock Physics And Its Applied Research

Seismic Rock Physics is a interdisciplinary studies producing in traditional Rock Physics and the Prospecting Seismology,being praised as a "bridge" joining the seismic data(attribute parameter)with oil reservior property(elastic parameter),last more than ten years obtain recognition sufficiently and development speedily abroad. Seismic rock physics is devoted itself to clarify the intrinsic relations that the nature of rock and its pore fluid versus the seismic property parameter.Based on the systematic theory and media models of rock physics property such as elastic, viscoelasticity and anisotropy in rocks,the empirical relations between seismic attribute versus reservior property parameter are established.By uses of the techniques such as fluid substitution and prestack elastic parameter inversion and so on,the reference fundamentals on seismic data interpretation are supplied for subtle reservoir prospecting and remaining oil production monitoring.Forcefully accelerate the techniques development such as seismic lithology recognition,hydrocarbon detection and seismic reservior monitoring etc.The research and application of seismic rock physics is delay relatively at home, yet there is not the treatise systematically to expound the theoretical base and the applied research of seismic rock physics at the moment.In order to carry forward seismic rock physics research and application at home,uniting the applied research to subtle reservoir prospecting in belly of Zunger basin,this dissertation clarified the funda- mental definition,main substance,research mentality,and development tendency for seismic rock physics;expounded the basic theory,media models, empirical relations,and measurement techniques of seismic rock physics;the full process of applied research involved with the core sampled,measurement data analysis,elastic parameter compares,empirical model building,fluid substitution, prestack seismic inversion,and reservior oil/gas prediction are discussed systematically.Many researched achievements are acquired including innovative method research results and applied research results. By means of compared with research target and substance of tradition rock physics and petrophysics analysis,clarify the fundamental definition of seismic rock physics,propose a news term "seismophysics" to state the seismic rock physics.At the same time,the development course and domestic research present situation were briefly reviewed to the angle through the petroleum industry demand promotion; analyse the development tendency;point out the development orientation for seismic rock physics.According the real demand of seismic data interpretation to rock physics, research to divide seismic rock physics into basic research and applied research. Moreover,expound the concrete substances of the two parts.First clearly and definitely propose the research mentality of seismic rock physics applied research:①Rock physics property parameter testing for core samples and its pore fluid simulated to keep the temperature and pressure in reserve in the laboratory;②Rock physics analysis(consist of the elastic parameter)for samples test data,empirical relation models established between different rock physics parameter versus the seismic attribute parameters;③Empirical relation models scaling with logging interpretation, and seismic attributes fluid-sensibility analysis combined with seismic forword modeling;④Fluid substituting and AVO modeling based on isotropy and anisotropy prospecting for reservior;⑤Reservior characterization and hydrocarbon detection by use of the prestack seismic elastic parameter inversion and so on.First more systematically expound the basis theory of seismic rock physics at home,consist of different type of media models,empirical relations,and measurement techniques and so on.In "Effective-Medium Model" section,the stress was analysed the assumptions and limitations for volume average model, self-consistent model,and scattering theoretic model,Expound the self-consistent approximations to two-phase media,heterogeneous media,the geometry description to different shape inclusion,and the mathematic expression to a cracked media.In "Machanism of Acoustic Propagation in a Fluid Saturated Porous Media" section,the kernel substance of seismic rock physics,emphatically expound Gassmann's relations, Biot's theory,Squirt(local flow)mechanism,BISQ(Biot-squirt)model and Patchy saturation model,and what based on fluid flow mechanism.Comparative analysis attenuation and dispersion mechanism expressed in distinct model.In "Seismic Property of Fluid" section,from the angle of applied research introduce in some expressions for calculating the fluid seismic property in porous rock(Batzle and Wang, 1992),clarify the prediction methods to fluid property parameter such as fluid density and bulk modulus along with the adaptive changes of temperature and pressure.In "Analyzing for Velocity Effects(Empirical Relations)",many empirical relations was expounded in seismic wave velocity effected from pressure,temperature,rock density, porosity,clay content,saturation,and correlated common empirical relation models, along with V_P-V_S relations and rock anisotropy research in laboratory.Finally introduce the new progress in test methods and simulation techniques such as the artificial rock sample(CIPS)and the digital image analysis(virtual digital test)and so on.In view of actual demand from the subtle reservoir prospecting on the belly in Zhunger basin,seismic rock physics applied research was carried out.More than 130 target rock samples was collected from 10 wells on the 4 tracts in research area.One complete of set rock physics test data was gained from these samples testing for different fluids-saturated at the temperature and pressure in reservior.By means of the test data systematically analysis,total variation regular and correlation relations between rock physical property parameters and elastic parameters was revealed,the seismic rock physics model was established in the research area.On the basis of the rock physics research results,integrated actual logging data,the fluid substitution modeling and the seismic elastic parameter inversion was launched.The hydrocarbon -bearing predicted map on Jurassic target was given out in the research area.Finally, above the complete acquired achievements summing up,proposed several understands and inspirations,pointed out some defects in this research work yet.Seismic rock physics applied research on the reservoir of belly in Zhunger basin acquired mainly 16 term achievements among which included 6 significant blazing new trails.●Three method research blazing new trails(1)The quantitative analysis on velocity changes with different fluid-saturated reveals firstly the total velocity variation regular when different fluid-bearing sandstone reservior in Sangonghe formation in the research area.As compared to velocity average measurements of dry bed(either gas-bearing bed),the V_P of oil-bearing bed and V_P of water-bearing bed all increase about 5%,the V_S of oil-bearing bed get higher a little(＜1%),and the V_S of water-bearing bed decrease about 2.5%.In oil-bearing bed,the lower is porosity of sandstone,the higher is V_P increase(from 4.2%up to 5.6%),and the lower is V_S increase(from 1.5%down to 0.8%).The V_P increase or decrease of water-bearing bed against dry bed is not related with sandstone porosity obviously.(2)In order to probe on basis of fluid detection from seismic data,and solved the actual demand for sand body prediction and hydrocarbon detection in the research area at the same time,fluid sensitivity comparative analysis of rock elastic parameter was carried out creatively.On the basis of V_P,V_S and densityρmeasurements,the rock elastic parameters as velocity ratioγ,compressional wave impedance Z_P,shear wave impedance Zs,Poisson ratioσ,bulk modulus K,shear modulusμ,Yang's modulus E,compressional wave modulus M,Lame coefficientλand compressional coefficientβwere calculated.By means of the argument sufficient diagram, quantitatively analysis was made to compare the relative change scopes of every elastic parameter for distinguishing "gas/oil","oil/water" and "gas/water".(3)Based on physics definition of the elastic moduli and elastic parameter with Biot-Gassmann's theory and the rock mechanics,above the comparative analysis of average measurement divergences from the elastic parameter changed relatively with the fluid altering,one creative idea that raising the detectiom capabilities for reservior fluid was proposed by use of the parameter array that choosing a modulus either parameter obviously dependent on rock frame nature to remove the frame effects in another modulus either parameter obviously dependent on fluid nature in rocks.By means of much kinds of pair-comparisons parameter array testing,that the resilience compose,finally the most optimization array as elastic moduli ratio Kμand elastic coefficient ratioλ/μwas chosen out to detect the reservior fluid in research area.●Three applied research blazing new trails(1)Through rock physics testing and analysing under partial saturation condition, First fined the variation tendency in reservior velocity changes with the water saturation against the rock porosity in research area.The P-wave velocity of sandstone gets higher slowly with the water saturation increase,as water saturation from 0 up to 1, The V_P variance ratio of different porosity rock samples is 2.60%(φ＜10%),2.49% (φ:10～15%)and 1.35%(φ＞15%)separately.The lower porosity of sandstone is, the higher V_P increase is obviously.S-wave velocity V_S get lower a little with the water saturation increase,there is not the obvious statistics relations against the rock porosity.This test cognition accord with Biot's theory and Gassmann's equation prediction completely.(2)The significant technique in seismic rock physics analysis——fluid substitution was first adoptd in the research area to simulate the feature changes of seismic responds with different hydrocabon saturation in reservior.Aimed at a gas/water bed of 21m thickness among Cretaceous and a oil/water bed of 11m thickness among Jurassic in the Y1 well,the "water→gas" substitution and "water→oil" substitution was carried on three kinds of gas saturation and three kinds of oil saturation separately.Fluid medium substitution and three kinds Han's oil saturation degree Fluid medium substitution.Deduce the detailed calculation process of fluid substitution.Give out the virtual logging curves of dencity and velocity,and synthetic seismograms under three kinds of saturation after fluid substitution.The feature changes of seismic responds with different hydrocabon saturation in reservior were discussed.(3)First having establish the seismic rock physics models(including the applied limitations for various empirical relations)of Sangonghe formation Jurassic reserviors in belly of Zhunger basin.Consist of velocity-pressure relations,velocity-temperature relations,velocity-dencity relations,dencity-porosity relations,permeability -caly content,V_P-V_S relations with different hydrocabon saturation in reservior. Along with the fluid sensitive parameters or parameter array for reservior hydrocarbon detection in the research area.Give out the 3-D prestak inversion results of elastic coefficient ratioλ/μ,together with the hydrocabon prediction plan view to Xishanyao-2 formation in the Y1 well.