APPLICATION OF SINGLE SANDLAYER GEOLOGIC CURVATURE ANALYSIS TO FRACTURE PREDICTION

As a traditional fracture-predicting method,curvature analysis was gradually improved in the long period of application. The geologic curvature used in this paper is a new kind of curvature-calculating method for geologic layers,which processes strictness in mathematics and practical significance in geology. The geologic targets of this research are three sandlayers with stable distribution laterally in a certain Jurassic formation. The previous research of this area investigated fracture distribution rules by the supersurface structural map of the overall formation;only a series of simple and qualitative conclusions were obtained about the relation between structure and fracture distribution. To reveal the controlling effect of structure upon fracture distribution,the structural map of each sandlayer supersurface was interpreted accurately with three-dimensional seismic data,the supersurface geologic curvature of each sandlayer was calculated with the new improved geologic curvature-calculating method,and the geologic curvature values were used as fracture-predicting parameters. Research outputs indicate that there are apparent differences between the distribution rules and values of geologic curvature for each sandlayer,the overall difference among the curvature values of each sandlayer has a very good matching relation with the overall difference among the production capacity of each sandlayer,and fine statistical relation exists between the natural production capacity and geologic curvature value of each well point in each sandlayer. Curvature analysis proved the existence of compound structures in the study area,and revealed that fractures often develop in the superimposed of structures. All this conclusions are of significance for fracture prediction before drilling.