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这种设备基本上由这些部分组成:一个变速推动系统,使岩样在屏蔽的伽傌射线源和屏蔽的闪烁探测器之间移动;一个光学测径仪,用以测量岩样的厚度;以及一架模拟计算机,从测得的参数计算密度和孔隙度。对于样品测得的厚度和算得的密度与孔隙度记录在条带图幅上。因为样品和图幅是以相同速度推动的,就能把记录的参数和样品作直接的比较。并且,为了和试验室岩心孔隙度测量作比较,提供了样品的累计孔隙度。这个Grape(伽傌射线衰减孔隙度估价仪)系统能适应多种应用。它被设计用于现场或试验室,而且只需一个操作员。这一设备可以以每分钟超过3时的推动速度处理直径l时到41/2时的岩心,惯常的岩心柱(core plugs)(指通常加工的小圆柱体岩心——译者)以及切片岩心(Slabbed core)。在这种速度下,对于100呎长的岩心可以在约6小时作出密度和孔隙度的分析。这个系统的误差,包括源强度的统计变化,在20％的孔隙度水平误差小于±1％孔隙度。几百呎的岩心(砂岩和碳酸岩)曾用这种连续设备作了孔隙度分析,和惯常试验室孔隙度比较的结果是优良的。虽然这个设备是为了测定石油勘探获得的沉积岩的密度和孔隙度而设计的,在其它方面的应用是可能的。这里包括:未固结的沉积岩样品和Teflon柱塞的孔隙度测定,油页岩样品油含量的测定,在观察井中侵入流体的饱和度的测定和成分的识别,以及对采矿工业中钻取的岩心或岩石样品矿体含量的测定。
The device consists essentially of a variable speed propulsion system that moves a rock sample between a shielded gamma ray source and a shielded scintillation detector, an optical caliper to measure the thickness of the rock sample, and An analog computer calculates density and porosity from the measured parameters. The thickness measured for the sample and the calculated density and porosity are recorded on the strip chart. Because the sample and map are driven at the same rate, the recorded parameters can be directly compared to the sample. Also, the cumulative porosity of the sample is provided for comparison with laboratory core porosity measurements. This Grape (Gamma Ray Decay Porosity Evaluator) system accommodates a wide range of applications. It is designed for use in the field or laboratory, and requires only one operator. This device can handle cores from 1 to 41/2 at a push speed of more than 3 o’clock per minute, the usual core plugs, and slicing cores (Slabbed core). At this rate, density and porosity analysis can be done in about 6 hours for a 100-foot-long core. The systematic errors, including statistical changes in source intensity, are less than ± 1% porosity at 20% porosity. Hundreds of feet of cores (sandstone and carbonate) were used to make porosity analyzes using this continuous system, which is superior to conventional laboratory porosity. Although this equipment is designed to determine the density and porosity of sedimentary rocks obtained from petroleum exploration, other applications are possible. These include: Porosity determination of unconsolidated sedimentary rock samples and Teflon plugs; determination of oil content in oil shale samples; determination of saturation of intrusive fluids in observation wells and identification of constituents; and drilling in the mining industry Core or rock samples - Determination of ore content.