Automatic Identification of Cracks from Borehole Image Under Complicated Geological Conditions

Identifying cracks from the spread image of a borehole wall is one of the most common usages of borehole imaging method. The manual identification of cracks is time-consuming and can be easily influenced by objective judgment. In this study, firstly, the image translation from RGB color model to HSV color model is done to highlight the structural plane region, which is closer to the color recognition of human sight; secondly, the Saturation component is filtered for further processing and a twice segmentation method is proposed to improve the accuracy of automatic identification. The primary segmentation is based on the statistics of saturation over a longer borehole section and can give a rough estimation of a crack. Then, the pixels are shifted in the reverse direction to the sine curve estimated and make the centerline of the crack flat. Based on the shifted image, the secondary segmentation is done with a small rectangle region that takes the baseline of the roughly estimated crack as its centerline. The result of the secondary segmentation can give a correction to the first estimation. Through verifying this method with actual borehole image data, the result has shown that this method can identify cracks automatically under very complicated geological conditions.

Predict sandstone distribution by integrated study of deformed shale using borehole image and seismic data,a case study from northern Gulf of Mexico

Many Upper Tertiary reservoirs from the Gulf of Mexico(GoM)are sandstones deposited either in channel-levee systems or lobe systems in the intra-slope deepwater environment.One of the major uncertainties about those reservoirs is their distribution,which is likely controlled by salt tectonics.The current salt structure,however,does not represent the salt structure when the sands were deposited.It is difficult,if not impossible,to restore the salt history based on current salt structures.Salt movement resulted in a great amount of deformed shale in GoM.Borehole images on the other hand can be used to characterize the internal structure or texture of deformed shale;and the dips of deformed shale from borehole images may be used to define the paleo slope direction,which controls the movement of deformed shale.The internal structure or texture of deformed shale,therefore,may provide some information about the history of salt movement,which may also control the sand distribution.In this integrated study,all the available data,including borehole images,seismic volumes,and other petrophysical logs,were used to characterize the reservoir sands and shales.The reservoir sands are mainly composed of amalgamated sand,layered sand,and laminated sandstone.Based on dips from borehole images,paleo flow directions of reservoir sands were defined.The shales are categorized as hemipelagic shale and deformed shale.The hemipelagic shale has relatively lower and consistent dips;whereas deformed shale has relatively higher variable in both dip magnitude and dip azimuth.The integrated study suggests the main reservoir of the field is submarine lobe sands deposited above an allochthonous salt in the basin.The evacuation of the salt body below the basin created small geographic lower area for sand lobes to accumulate.The dips from the deformed shale provided information about the center of the small(or mini)basin,thus established a relationship between the dip pattern and sandstone distribution.If this relationship is valid for the other upper Tertiary deformed shale in the GoM area,a new method can be developed,which may enable us to predict the sandstone distribution using borehole images and provide guidance for petroleum evaluation and field development in the future.

Coal and rock fissure evolution and distribution characteristics of multi-seam mining

Henan Pingdingshan No.10 mine is prone to both coal and gas outbursts.The E_(9-10)coal seam is the main coal-producing seam but has poor quality ventilation,thus making it relatively difficult for gas extraction.The F_(15)coal seam,at its lower section,is not prone to coal and gas outbursts.The average seam separation distance of 150 m is greater than the upper limit for underside protective seam mining.Based on borehole imaging technology for field exploration of coal and rock fracture characteristics and discrete element numerical simulation,we have studied the evolution laws and distribution characteristics of the coal and rock fissure field between these two coal seams.By analysis of the influential effect of group F coal mining on the E_(9-10)coal seam,we have shown that a number of small fissures also develop in the area some 150 m above the overlying strata.The width and number of the fissures also increase with the extent of mining activity.Most of the fissures develop at a low angle or even parallel to the strata.The results show that the mining of the F_(15)coal seam has the effect of improving the permeability of the E_(9-10)coal seam.