干湿循环作用下炭质泥岩溶蚀孔隙度的化学计量方法

为建立干湿循环作用下炭质泥岩溶蚀孔隙度的化学计量方法，对干湿循环作用后的炭质泥岩试样进行X射线衍射试验，测试干湿循环作用下炭质泥岩的矿物成份演变；同时，采用电感耦合等离子发射光谱测试技术，研究干湿循环作用下炭质泥岩浸泡溶液的离子浓度变化规律；基于离子守恒定律，推断干湿循环作用下炭质泥岩矿物发生的化学反应；在此基础上，建立浸泡溶液离子浓度与炭质泥岩矿物反应量的定量关系，并计算炭质泥岩各矿物反应的体积；基于唯象理论，提出以反应物与生成物的体积差为溶蚀孔隙体积增量，构建炭质泥岩溶蚀孔隙度的化学计量方法；最后，利用比重瓶法和核磁共振法对炭质泥岩溶蚀孔隙度的计算结果进行验证。结果表明：干湿循环作用下炭质泥岩的方解石、钾长石和钠长石含量减小，高岭石含量增加；随干湿循环次数增加，浸泡溶液中Ca²⁺、K⁺、Na⁺、Fe²⁺和Al³⁺离子浓度均增加，其中Ca²⁺离子浓度增长速率是其他阳离子的数十倍；经化学分析发现，方解石溶蚀和长石水解生成高岭石是干湿循环作用下炭质泥岩孔隙演...

A Stoichiometric Method for Dissolution Porosity of Carbonaceous Mudstone Under Dry and Wet Cycles

In order to achieve the chemical quantitative calculation of the dissolution porosity of carbonaceous mudstone under dry and wet cycles. The X-ray diffraction testing methods was used to research mineral evolution of carbonaceous mudstone under dry and wet cycles. Using inductively coupled plasma emission spectrometer to measure the ion concentration of carbonaceous mudstone soaking solution. Based on the principle of ion conservation, the chemical reaction of the carbonaceous mudstone under the dry and wet cycles is analyzed. On this basis, a quantitative relationship between the ion concentration of the soaking solution and the reaction amount of carbonaceous mudstone minerals is established, and the reaction volume of each mineral of the carbonaceous mudstone is calculated theoretically. Based on the phenomenological theory, assuming the volume difference between reactants and products as the volume increment of dissolution pore, a stoichiometric method for dissolution porosity of carbonaceous mudstone is constructed. Finally, the calculation results of the porosity of the carbonaceous mudstone with different dry and wet cycles were verified by the pycnometer test and nuclear magnetic resonance test. The results show that the content of calcite, potash feldspar and albite in the carbonaceous mudstone decreases under dry and wet cycles, while the content of kaolinite increases. With the increase of the number of dry and wet cycles, the concentration of Ca²⁺, K⁺, Na⁺, Fe²⁺ and Al³⁺ in the solution are increase, and the growth rate of the Ca²⁺ ion concentration is dozens times than other metal cation. The calcite is dissolved and the feldspar is hydrolyzed to form kaolinite, which are the important causes of pore initiation in the carbonaceous mudstone under dry and wet cycles. The test certificated that it is a feasible method to use mineral ion concentration to quantitatively calculate the dissolution porosity of carbonaceous mudstone, and which provides a new way to quantitatively study the evolution of soft rock pores under dry and wet cycles.