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Abstract

An apparatus that enables spot measurements of permeability variations along a core measuring 2 permeability variations along a core measuring 2 inches in diameter and 5.5 inches in length was developed. The apparatus is based on liquid injection at the rock surface and is referred to as the "Liquid Minipermeameter" (LMP). During the LMP measurements are also compared against air minipermeameter measurements. During liquid injection using the LMP, flow patterns were studied through the injection of colored liquids.

Various formation damage mechanisms on consolidated rocks using conventional coreflooding apparatus have been studied in conjunction with LMP measurements. LMP measurements were conducted before and after the formation damage experiments. The present paper includes an interpretation of a complex formation damage mechanism involving precipitation of gelatinous iron hydroxide. In this precipitation of gelatinous iron hydroxide. In this case, spot permeability measurements provide valuable information on the extent of damage as it is shown from LMP spatial variations. Advantages of the LMP measurements arise as the measurements are not destructive for the rock sample and the rock heterogeneity is not excluded from the interpretation of the formation damage experiments. Compared to air minipermeameter the LMP shows better repeatability while drying of the rocks is not necessary.

Introduction

The purpose of studying various formation damage mechanisms is to improve the well productivity or injectivity for producing and injecting wells. respectively. In some other cases, formation damage is studied as a tentative method to divert flow from zones of high permeability, in the case of injection wells. In our study various formation damage mechanisms are considered as methods of destroying the reservoir permeability through injection at watered-out wells. This permeability reduction will reduce the amount of water influx at the center of a gas field that has a strong edge-water drive mechanism. In trying different reactive fluids in the laboratory on rock samples, conclusions can be made on the effectiveness of different damage mechanisms on reducing the permeability of the rock as it is recorded from the increase in pressure difference at the two ends of the rock. However, no conclusions can be derived on the extend of the damage in the rock, i.e. how far from the injection end the rock is damaged.

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