Rock Permeability Measurements Using Drilling Cutting

Abstract The current available equipment used in the laboratory to measure permeability of the core samples is very limited. This is because permeability is measured only in one dimension and the faces of the core samples are damaged due to the grain repositioning during sample cutting. The only way to measure permeability is by using a nondamaged sample by chipping it off from the rock. This situation occurs only with drilling cutting samples. New laboratory equipment was designed to measure permeability of the cutting samples. A probe is used in this equipment which is easy to change to accommodate different cutting sample sizes. While using any cutting samples, three different perpendicular points are used and their permeability values measured. When two permeability readings are identical, they quantify the plane permeability. This method of permeability measurement is considered more realistic because: most of the cutting faces are minimally damaged. This equipment is very simple to use, operate and maintain in the laboratory. The equipment is light and portable and can also be used in the field. Introduction The current permeameters used in the oil industry to measure rock permeability require core samples of certain length and diameter. For example, the gas/liquid permeameter require core samples of 1.5 × 1.0 - core sample size. During cutting in the laboratory most part of the core sample is invaded by the water used to cut the sample. The presence of water and core cutters causes certain damage to the faces of the core samples. Sharpening the inlets and outlets of the core sample using core cutter cause repositioning of the gram. This occurs while a gram is removed during cutting and repressed or positioned as water flows over the edge. This gram repositioning causes the reduction of permeability. On the other hand, if the water used to cut the core sample is incompatible with the clay stability in the core, this clay may swell causing permeability changes. Permeameters that use pressure decay on a long core sample have the same problems('). In addition, this type of equipment can measure permeability in two directions only. As a result, permeability of the core samples does not represent the real rock permeability. Experience showed that core samples permeability is in the range 6570% of the real permeability. This is based on comparing the measured permeability to the calculated permeability from logging data. The Core Measurement System (CSM) has the same disadvantage. Since core samples have high level of heterogeneity, either an average permeability can be calculated or certain points should be chosen along the core sample(2l. The rock heterogeneity is a good reason for getting permeability from cutting samples since they are available. Permeability can also be calculated from well testing data, however despite being more accurate, this method is quite expensive. Another way to measure permeability is by using formation tester from service companies. However, in the vicinity of packer in the high permeability rock the drawdown pressure is too small to be accurate.