利用声波反演技术识别储层流体性质

Recognition of reservoir fluid property by acoustic logging inversion

储层流体性质识别是测井解释的重要内容之一.在钻井过程中,储层所含流体性质一般在录井岩屑或钻井取心中能够直接定性识别,但录井岩屑和岩心受到井内泥浆等因素的影响,无法准确评价.有些测井技术,例如核磁共振成像测井,可以直接测量储层流体性质,但由于费用问题,不可能对所有井进行核磁共振测井.为此,本文研究如何利用常规声波测井方法进行流体性质识别.首先建立流体识别模型,根据模型把声波时差反演成电阻率值,再用反演电阻率和实测电阻率进行比较.当实测电阻率大于反演电阻率时,储层为气层;当实测电阻率小于反演电阻率时,储层为水层;气水同层和含气水层介于气层和水层之间,可根据实测电阻率和反演电阻率的差值大小来判别.实例表明,该方法适用于孔隙度较高的储层,孔隙度越大,流体判别的准确性越高.对低孔裂缝性储层及储层物性较差时,效果较差.

The recognition of reservoir fluid property is one of the important contents of logging interpretation.In the process of well drilling,the property of the fluid contained in the reservoir can directly be recognized from logging cuttings and cores.But because the logging cuttings and cores may be polluted,and accurate result is not easily obtained.Some logging techniques,such as NMR imaging logging,can directly measure the property of reservoir fluids,but this logging technique can not be applied to all wells because of its high cost.For solving the difficulty,it is studied how recognize the property of reservoir fluids by conventional acoustic logging technique.At first,the models for the recognition of the reservoir fluid property are established,then acoustic interval transit time is inversed into resistivity according to the models,and the inversed resistivity compares with the measured resistivity.If the measured resistivity is greater than the inversed resistivity,the reservoir is gas layer;if the measured resistivity is less than the inversed resistivity,the reservoir is water layer;the resistivity of the layer containing gas and water at the same time and the water layer containing gas is between that of gas layer and that of water layer,and they can be recognized from the magnitude of the difference between the measured resistivity and the inversed resistivity.some cases show that this method is suitable to the recognition of fluid property in the reservoirs of great porosity,the greater the porosity,the more accurate the recognition.For the reservoirs of low porosity and low permeability,the result of this method is poorer.