四川盆地建南地区二叠系长兴组生物礁滩储集层预测

Prediction of reef and bank reservoir of the Permian Changxing Formation in Jiannan area,Sichuan Basin

四川盆地建南地区长兴组生物礁滩储集层分布受控于开江—梁平盆地的展布,但对于该区盆地的延伸范围一直存在多种观点。作者通过深入研究礁滩在地震剖面上的响应特征,主要利用钻井资料并结合正演模型,发现研究区内茅口组四段顶部灰岩厚度与TP2地震反射层形态有关。由于在茅口组末期研究区内存在东吴抬升运动,古地形高地遭受强烈剥蚀,茅口组四段顶部灰岩残余厚度小,对应的地震剖面出现"双强"反射特征;反之,古地形低处遭受剥蚀少,茅口组四段顶部灰岩残余厚度大,对应的地震剖面出现"三强"反射特征。利用此特点建立古地形和地震属性之间的关系,通过分析发现茅口组沉积末期研究区内呈现出西低东高的构造格局。由于长兴初期开始受构造运动影响,开江—梁平盆地逐步拉张,到长二末期形成了新的古地貌。利用地层切片技术、野外露头资料、薄片及钻井资料分析,认为盆地从中间穿过研究区。结合构造运动及现有资料证据,综合物探和地质资料提出了一种盆地分布范围的新观点,并确定了适合生物礁滩发育的有利区带。

The distribution of reef and bank reservoir of the Changxing Formation in Jiannan area is controlled by the distribution of the Kaijiang-Liangping Basin. The response characteristics on seismic pro- file of the reef and bank were studied. Mainly on the basis of drilling well data and forward simulation model, the research results indicate that the thickness of limestone of the Member 4 of Maokou Formation is related with the shape of TP2 seismic reflection interval. During the late period of Maokou Formation, the Dongwu tectonic movement occurred in the study area which led to the intensive stratigraphic exposion.The remnant thickness of limestone of the top Member 4 of Maokou Formation was thin and led to the ＂two intensive＂ reflection on seismic profile. In contrast, less exposion occurred at lower paleotopographic unit. Thus the remnant thickness of limestone of the Member 4 of Maokou Formation was thick and the corre- sponding seismic reflection is characterized by ＂three intensive＂ reflection. The relationship between pal- eotopography and seismic attributes was established using this characteristic. The analyses show that the tectonic framework is characterized by ＂lower in west and higher in east＂ in the late depositional period of the Maokou Formation. Due to the influence of tectonic movement in the early period of Changxing Forma- tion, the Kaijiang-Liangping Basin gradually expanded and formed a new paleotopography in the late depo- sitional period of submember 2 of Changxing Formation. By the analyses of stratigraphic slice data, outcrop and drilling well data, the authors propose that the basin crossed the study area. A new viewpoint about the distribution of the basin has been proposed and the profitable developing area of reef and bank has been identified combining with tectonic movement and current data and the comprehensive geophysical and geo- logical data.