考虑岩石润湿性的新导电模型研究

On a New Conducting Model Combining Rock Wettability

考虑岩石的润湿性 ,用连续函数模拟油珠表面和孔隙表面的接触关系 ,提出了新的岩石导电模型 (CWRM )。当油珠进入具有不同孔喉尺寸岩石模型后 ,由于岩石具有的润湿性 ,油珠和岩石孔隙表面可能具有不同的接触方式。在水润湿性的储层中 ,油珠和孔隙表面之间会有水膜 ,水膜保持了连续的导电路径 ,因此 ,水润湿性岩石中常会形成低电阻率。相反 ,在油润湿性岩石中 ,油珠与岩石孔隙表面紧密接触 ,可能完全堵死孔喉 ,导致岩石电阻率异常地增高。所以 ,即使在含油饱和度相同的情况下 ,岩石的电阻率也会因为润湿性不同而显著地变化。根据阿尔奇公式和CWRM模型 ,在考虑岩石润湿性的情况下 ,计算了岩石模型的含水饱和度。计算结果表明 ,使用阿尔奇公式和CWRM计算的含水饱和度 ,其差值可达 10 %或更高。对于水润湿和油润湿岩石 ,根据CWRM计算的I -Sw 关系在双对数坐标中都是曲线关系。CWRM模型和结论均被野外数据和实验室数据所证实。

Archie' s Laws, as classic formulae, always play the key role in reservoir evaluation. Exploration technology for petroleum, however, is getting more complex. Thus, more and more experts pay attention to such effects as pore structure and wettability on resistivity measurements, and how to evaluate the effects is still a problem. Having taken the wettability into account and simulated the surface of oil drop and the contact way between oil drop and pore with continuous function, this paper presents a new conducting model (CWRM).When oil drops are driven into a rock model with pores in different size, the oil drops may contact the surface of pores in different way if the rock holds water and oil wettability, respectively. In water-wet reservoir, there is a water film between the oil drops and the surface of pore. It's the water film that may lead lower resistivity in water-wettability rock because the water film always keeps current circuit continuous;In oil wet reservoir, on the other hand, pore throats may be blocked entirely to current flow because the oil drops contact the surface of pore directly, which causes rock resistivity increase sharply. So, the rock resistivity may change significantly according to water and oil wet, respectively, even if the saturation estimate is kept the same. After water saturation estimate is calculated with Archie's Laws and the new conducting model (CWRM),the calculations show that the difference of saturation estimate between Archie's Laws and the new conducting model can be at least 10% or up. Instead of a straight line, the relationships of saturation estimate and resistivity index are flexural lines in log-log co-ordinate according to the new conducting model (CWRM). All the conclusions given in the paper are confirmed by field and laboratory data. So CWRM presented in the paper offeres a method to improve the precision of saturation estimate.