Henn François, Durand Claudine, Cerepi Adrian, Brosse Etienne, Giuntini J C
Laboratoire de Physicochimie de la Matière Condensée, UMR 5617 CNRS, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
J Colloid Interface Sci. 2007 Jul 15;311(2):571-8. doi: 10.1016/j.jcis.2007.02.062. Epub 2007 Apr 11.
Low resistivity in argillaceous sandstone reservoirs may be attributed either to the effect of microporosity, or to specific effects due to intrinsic clays' conducting properties or to other conducting minerals. In order to distinguish these effects, cation exchange capacity, specific surface areas, and dc conductivity of various pore lining chlorite-bearing sandstones from different hydrocarbon reservoir measurements are investigated. Cation exchange capacity and specific surface area are measured on whole rocks as well as on size-separated fractions. Both sets of values are low, in agreement with the structural and textural observations. The conductivity of these chlorites, measured in air conditions and after dehydration, is investigated by means of complex impedance spectroscopy on size-separated fractions as a function of temperature and compared to that of reference clays. The results show a large influence of moisture, applied electric field frequency, and temperature on the electrical properties. The magnitude of the dehydrated clays' conductivity is such that its influence on the conductivity of argillaceous sandstone is lower than that related to the presence of water or brine by several orders of magnitude. The dc conductivity and the related activation energy of the dehydrated samples appear to be related to the chemical composition of the clays. More specifically, a clear correlation occurs with the electrical charges of the clay network, that is to say with the location, i.e., tetrahedral or octahedral sites, of the substituting trivalent elements.
泥质砂岩储层的低电阻率可能归因于微孔孔隙度的影响，或者是由于原生黏土的导电特性或其他导电矿物所产生的特定影响。为了区分这些影响，对来自不同油气藏测量的各种孔隙衬里含绿泥石砂岩的阳离子交换容量、比表面积和直流电导率进行了研究。阳离子交换容量和比表面积在整块岩石以及按粒度分离的组分上进行测量。两组数值都很低，这与结构和纹理观测结果一致。通过复阻抗谱对按粒度分离的组分作为温度的函数，在空气条件下和脱水后测量这些绿泥石的电导率，并与参考黏土的电导率进行比较。结果表明，湿度、外加电场频率和温度对电学性质有很大影响。脱水黏土的电导率大小使得其对泥质砂岩电导率的影响比与水或盐水存在相关的影响低几个数量级。脱水样品的直流电导率和相关活化能似乎与黏土的化学成分有关。更具体地说，与黏土网络的电荷存在明显相关性，也就是说与替代三价元素的位置（即四面体或八面体位置）有关。
