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This paper reveals new information on the reduction in productivity caused by the crushed zone surrounding a jet perforation tunnel. A Berea sandstone sample was perforated according to a slightly modified API RP 43 Recommended Practice Standard Procedure for perforation, using a 3.5 gr. RDX type charge. The crushed zone was identified using a scanning electron microscope, SEM. The crushed zone was divided into a number of cells both radially (away from the shot center) and longitudinally (along the perforation tunnel). Porosity and permeability of each cell were obtained using image analysis. The permeability value of each cell was arranged around the perforation tunnel according to their original orientations. U sing a black oil simulator, productivity of a well was found and compared to one where no permeability reduction was assumed for the crushed zone. In addition, the Dykstra-Parsons relation was employed to estimate permeability values for a suite of 20 cells. The estimated values were then oriented around the perforation tunnel in ascending, descending, and randomly orders. Productivity of the well was obtained for each permeability orientation. A 55% permeability reduction around the perforation tunnel, as the result of the perforation process, led to a 60% reduction in well productivity. Also, ascending orientation of the permeability around the perforation tunnel resulted in a higher well productivity than descending or random orientation.

Summary This paper presents a method to measure porosity and permeability alteration of the porosity and permeability alteration of the crushed-zone using scanning electron microscopy (SEM) and image analysis. A new phenomenon, shock metamorphism, was shown phenomenon, shock metamorphism, was shown to exist and is believed to be useful to evaluate shock wave penetration. Berea sandstone samples were prepared using a modification of the older API-43 recommended practice for test sample preparation. Samples were perforated preparation. Samples were perforated using low and medium penetration shaped charges. Analysis of the low charge shot sample indicated an average porosity reduction of 25%, and an average permeability reduction of 55% within the permeability reduction of 55% within the crushed zone. The sample shot with the medium penetration shaped charge showed planar element shock metamorphism. Introduction Shaped charge jet perforation is the most widely used method of establishing flow pathways from an oil or gas formation to the inside of a wellbore in oil and gas producing wells. A primary objective of producing wells. A primary objective of the jet perforation process is to create "clean" regularly shaped holes or tunnels that have a high fluid flow capacity. In shaped charge jet perforation, the detonation of an explosive charge containing a conical depression creates a sharply focused intense pressure pulse that can exceed 4 × 10(6) psi. and have a velocity of 30,000 ft/second. This pulse of hot explosion gas pushes aside all materials in its way. As effective as this process is in creating a hole or tunnel, it also alters the rock formation around the 1/4 to 1/2 inch diameter tunnel which is created, as indicated by Bell. This "altered" or "compacted" or "crushed-zone" is believed to be responsible for permeability of this zone being significantly less (up to 70% less) than virgin formation. Several authors have noted the presence of this crushed zone and also studied the effect of the compacted zone on well productivity both experimentally and productivity both experimentally and theoretically. However, their results were not based on direct measurements on the crushed zone. Bell indicated that formation strength, explosive charge shape, charge size, and operating configuration in the wellbore are known to affect shot penetration. But the effect of each of penetration. But the effect of each of these variables on the nature and extent of the crushed zone has not been reported, probably in large part due to lack of an probably in large part due to lack of an experimental methodology to directly observe the crushed zone.

The digital computer is undeniably an asset in the examination of many classes of geologic problems. Unfortunately, it is ill suited for handling pictorial in formation which constitutes a large percentage of geologic data. For certain kinds of problems, the inherent physical properties of optical lenses can be used to perform analyses that are impractical using a digital approach. For example, in a current study of pore structure in reservoir rocks, the pore pattern of an area 24 x 24 millimeters on a thin section was digitized, yielding more than one million data points. Spectral analysis was used to determine the relative contri butions of spatial frequencies to the total porosity, but even with the Fast Four ier Transform, a two-dimensional spectral analysis of a single thin section is very expensive even on a large computer. In contrast, a proper optical lens system will produce a Fourier transform and map the power spectrum on film in a few seconds. A digital approach is more expensive by three or four orders of magni tude. Optical-processing methods are especially well suited for study of radar imagery air photographs and gross fabric patterns, as well as microscopic textures in rocks. 50 DAVIS AND PRESTON

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