川东北气田储层微量元素及沉积环境分析

海相沉积碳酸盐岩微量元素值域变化对了解古海平面起伏变化、气候条件和及古沉积海水温度具有较大的意义。以PG1井为检验井,取其储层岩芯样品共计122组,分析微相元素纵向演化特征,判识其沉积环境。实验分析表明:Ca/Mg比值从下至上逐渐增大、飞一~飞二段边缘浅滩相的Ca/Mg值(约1.2)小于飞三段的潮坪相的Ca/Mg值(约2.0),说明飞一、飞二段白云化程度高于飞三段;因此其白云化岩较发育,是优势储层。长兴-飞仙关组Sr、Mn、Fe元素含量分别位于80~500μg/g、7~90μg/g、0.6%~1.4%之间,具有高Sr,低Fe、Mn的特征,二者白云岩化流体具有同源性,反映其白云岩成因是在封闭、淡水没有参与的体系下形成。研究认为:川东北晚二叠世-早三叠世气候非常干旱赤热,强烈的蒸发作用导致沉积物中的孔隙水及海水盐度慢慢增大,Mg2+逐渐置换了水体中的Ca2+离子,不仅有利于碳酸盐岩发生准同生白云岩化作用,同时有利于在台地两侧高能边缘礁滩沉积环境中发生埋藏白云岩化作用。

Analysis of trace elements and sedimentary environment of reservoir in Northeast Sichuan Gas Field

marine sedimentary carbonate rock trace elements range change of understanding sea-level fluctuations, climate conditions and sedimentary paleo seawater temperature has great significance. In this paper, the PG1 well is a test well, and a total of 122 sets of core samples are taken, and the longitudinal evolution of the micro facies is analyzed. Experimental results showed that the Ca / Mg ratio from the first increases gradually, fly a ~ fly a shoal facies on edge of Ca / Mg value (about 1.2) less than fly three segments of the tidal flat of Ca / Mg value (about 2.0), indicating that the fly, fly to the second period of dolomitization degree higher than fly three sections, so the dolomitic rocks is developed, is predominant reservoir. Changxing - Feixianguan SR group, the content of Mn and Fe elements are located in between 80 to 500 g / g, 7 ~ 90 g / g, 0.6% ~ 1.4%, with high Sr, low Fe, Mn and two dolomitizing fluids with homology to reflect the genesis of dolomite in closed, fresh water is not involved in the system form. Studies suggest that: Northeast Sichuan late Permian - Early Triassic climate is dry and red hot, intense evaporation lead in sediment pore water and seawater salinity increases slowly and Mg2 + in the gradually replaced the water of Ca2 + ion, is not only conducive to carbonate rocks occur quasi syngenetic dolomitization, and helps in on both sides of the platform edge high-energy reef and shoal sedimentary environment occurred burial dolomitization.