The Measuring Instruments Of Core Gas Permeability Based In Steady Pressure

The core permeability of hydrocarbon reservoir is an important physical parameter index which can measure the size of the permeability reservoirs, and accurately display the ability of reservoir which rock allows fluid through. No matter what we are engaged in oil and gas exploration, reservoir evaluation, or oil development, the core permeability is an indispensable physical parameter.Therefore, it’s very important and self-evident to accurately determinate the core permeability of Hydrocarbon reservoir.As is well known that core permeability is referred to the absolute permeability of rock with experiment method. When the direct determination of core permeability is talked about, there are three points should be follow in Darcy equation (which are single phase flow, lamellar flow and fluid and rock not react with each other). To use liquid rock permeability and determination to meet with the three point are often so difficult, so react with gas is usually measured core permeability in order to avoid fluid and rock react with each other, the using gas is commonly air.There are two kinds of methods can be used to measure the core permeability, which are unsteady state and steady state. Unfortunately, both of the methods have had serious shortage. It’s so difficult that people can not accurately measure the core permeability.In the unsteady method, flow pipe air measurement is commonly used in laboratory. There are a few different paragraphs in the flow pipe, and each paragraph has a valued B which is different from each other BS. Different pope line sections with different B are chosen to measure and calculate according to the different core permeability. When the lab standard core be measured for the same diameter pope line section of core values, in turn the B are different. So the valued B must be chosen in measuring core permeability. It’s too inconvenient to accurately measure the core permeability. To ensure the accuracy of the core permeability measurement results, the flow constant B should be regularly calibrate. Otherwise, it will affect determination of the core penetration.In the steady method, a high-pressure cylinders is commonly linked to the laboratory instruments. Because of the gas sliding effect, the measured core permeability becomes different with the different average pressure and gas slippage effect. Therefore, the method of measuring the gas permeability often vary from person to person, even sometimes different.In the basis of the principle of voltage, the new gas logging permeability instruments uses a inflatable built-in aerating pump making the import and export core pressure constant, and always maintain the core permeability error range in1%.The technology innovation of the designed instrument can be briefed as follows.(1) For the realizable way of the voltage regulation, a high-accuracy glass tube is used for air supply in here. With the mercury ring sealing technology, the removable piston can be sealed in the glass tube. When the piston moved in uniform, the pressure value of the air pump can be a constant.(2)The concept of the mercury ring sealing technology is that mercury metal(mercury) is liquid at room temperature, and the surface tension coefficient is500X10"3N/m, far larger than the other liquid coefficient, such as the surface tension coefficient of water is72.5X10"3N/m when the room temperature is20℃, and mercury can’t wetting the two kinds of materials that are plastic and glass. On the piston motion process, mercury can’t adsorption in glass wall caused by residual on According to the tension coefficient of the mercury itself, the mercury ring can be shaped in the piston and glass tube, which formed the mercury effect.(3) It’s a very important and difficult point to determine the pressure regulator, for the instrument must be able to measure the core permeability in the range of a few MD to a few D by readable measurement. Therefore, the plastic piston of dozens of grams is displaced by the steel piston of dozens of kilograms, and the weight of the piston increases by a hundred times. Such a request by the pistons technology innovation of mercury ring seal to realize that the core of the piston processing and sealing technology had higher innovation requires.(4) In order to improve this instrument to low permeability core permeability test range, joining the soap membrane flow meter, so as to measure the range of lml/min-flow20ml/min of low permeability core measurements.In the automation of the new instrument, on one hand, a controllable inductive circuit is joined in, which realized a ONE-KEY type of opening and closing, and automatic measurement date collection, making more convenient and quick accurate measurement. On the other hand, in order to overcome the shortcomings of traditional soap membrane flow meter manual choke table in a soap timing, taken membrane flow pipe ends litter photoelectric inductive fleeing into joining clock, timing circuits to directly convert the flow and formula design more soap membrane flow meter of open, adjustable soap film diameter and photoelectric timing z position supporting shell, make soap membrane into bubble more convenient and more accurate.With the development of this new steady-state core permeability instrument of the constant pressure, many results can be realized as follows: (1)In the way of using a self-sufficient air supply instead of the external high pressure cylinders, the high-accuracy glass tube is in the well use of realizing the core inlet pressure.(2)For the research of mercury ring seal glass cylinder technology, the craft reference plastic piston infuse mercury sealing tests success.(3)Using the steal piston of1-2Kg weight instead of the plastic piston, machining precision plastic injection technology and testing reached experimental expected requirements.(4)In the circuit automation control, the measure sensitivity and response time, error are at a high accuracy by using photoelectric time control.(5)Through a lot of experiments of each instrument function components connect testing, while compared to the traditional measuring method and the same core, more accurately instrument stable test date can be had.