Research Of Predicting Methods Of Porous And Crack Reservoir

As the acending need of the oil and gas resources, the constant progress is goingbeing made in the exploration and development of oil and gas. The exploration key ischanging from tectonic exploration to lithological exploration. In deed, the complexsubtle reservoirs become the key point to explore. The porous and crack reservoirshave a great proportion. We must take good advantage of the superiority ofpre-stacked and post-stacked seismic data to describe this kind of reservoirs to seekmost valuable potential reservoirs, which can reduce the risk of exploration.Based on ancestors’ theoretical research and directed by the AVO theory ofpre-stacked azimuthal anisotropy and two-phase rock physics theory, we get aresearch in inversion methods for predicting cracks, porosity and pore structure, andwe test and apply the methods in real seismic data. And the detailed contents asbelow:(1) We do a lot of research in HTI media theory, Hudson crack theory andThomsen crack theory，and we fully comprehend the seismic wave propagationprocess in HTI media, vertical cracks in HTI media can affect seismic record in otherreflection strata as it is seen as disturbance in reflection seismic data. Thus in actualapplication, we should eliminate the anisotropic influence of nonstudied strata beforeother processes to the studied strata.(2) We do a lot of research, analysis and comparation to approximate reflectioncoefficients of P-P wave and P-SV wave in HTI media. From analytical results wecan conclude:①Influencing by the anisotropy of HTI media, RPSdistributes asellipse via the change of azimuth, whose property may indicate the fractured azimuthand intensity;②the anisotropic coefficient is nothing to do with RPP, but γhas greatinfluence to RPP;③but all the3anisotropic coefficients、、γ has certain influenceto RPS, and γ has great influence to RPS too;④RPSis more sensitive to fracturedmedia(HTI). To trigonometrical function expand RPS expression to an inversionfuction, and thus through which the crack azimuth and density are inversed. From theexpansion expression, RRSis mainly determined by P1、P2、P3，and directlyinfluenced by γ、 in P1、P2、P3expression. And it has been proved that the crackazimuth inversed by P2and P3is more precise. (3) Based on two-phase media theory, we study the factor of porosity likepore-type, diagenesis and so on. We set a unique rock skeleton model and itsexpression which contains both porosity and pore structure proposed in existing rockskeleton model by ancestors. Putting them into Gassmann equation, a new porosityand pore-structure inversion expression is found. The results of real seismic and welllogging data process show that the new inversion is effective and reliable.(4) We study parameters p and q in the unique rock skeleton we proposed, weget some inclusions: p and q can be defined as loose coefficient. As the ascending of pand q, stiffness of rock is descending, rock is softening, loosing. And thus the rockelastic parameters are changing with the changing of p and q. But the pore-structureparameter C is reciprocal to p and q. So when p and q is small but C is large, it isuseful to describe a potential reservoir.(5) From the porosity inversion expression based on pore-structure parameter,we can do partial derivative to rock saturation equivalent compressibility coefficientβEby porosity ε and pore-structure C respectively, which means we can know whichone has greater contribution to the rock elastic feature. We have made3situations todescribe the problem in use of the ratio or difference between the2partial derivative.When we link the problem to pore type in carbonate reservoir, we get the conclusionbelow: as the pore type is mainly stiff pore, rock saturation equivalent compressibilitycoefficient βEis mainly influenced by porosity, as the pore type is mainly crack pore,rock saturation equivalent compressibility coefficient βEis mainly influenced by porestructure.