川东北飞仙关组鲕滩储层分布规律、勘探方法与远景预测
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摘要
20世纪末在四川盆地东北部发现了渡口河等以孔隙性鲕粒白云岩为储层的飞仙关组气藏。这些储层的分布与飞仙关组鲕粒滩的分布规律有关。研究表明当时的古地理格局控制了飞仙关组鲕粒滩的分布 ,因而影响着鲕滩气藏的分布。研究区的鲕粒滩集中分布在环早期开江—梁平海槽的碳酸盐岩台地边缘 ,它们随着碳酸盐岩台地沉积区的扩大和开江—梁平海槽的消亡而发育迁移 ,形成了宣汉黄金口—开县地区、达县—梁平地区等几个鲕粒岩集中发育区块。由于孔隙性鲕粒白云岩的形成与混合水白云石化作用和深埋藏溶解作用有关 ,故储层呈大小不等的透镜状分布在致密的鲕粒灰岩中 ,使鲕粒气藏具有岩性—构造复合圈闭的特点。孔隙性白云岩储层的声速平均 5 5 4 0m/s,致密灰岩的大于 6 2 0 0m/s ,故在地震剖面上储层表现为在一定层位的弱反射背景出现的一段连续的强振幅反射。因此 ,鲕滩气藏的勘探可遵循“占边缘、找亮点、套构造”的思路进行综合预测勘探。除目前重点勘探的五宝场地区外 ,宣汉黄金口—万源区块和达川—梁平区块是很有希望的勘探后备区块 ,万源—南江区块和广元—昌平区块是鲕滩气藏勘探的远景区块。
In Dukouhe structure,etc.,some large and mediu m sized gas reservoirs which are composed of porous oolitic dolomites were foun d in Northeast Sichuan Basi n in the end of the 20th century,and the distribution of these reservoirs is rel ated to that of the oolitic beaches in Feixianguan Formation.Through research it is shown that the distribution of the oolitic beaches in Feixianguan Formation is controlled by the palaeogeographic pattern during Feixianguan Age,thus influe ncing the distribution of the oolitic beach reservoirs.The oolitic beaches in th e region are concentrically distributed along the carbonate platform edge of cir cum early Kaijiang Liangping trough.They were growing and moving along with th e enlargement of the carbonate platform sedimentation area and the elimination of the Kaijiang Liangping trough to form several developed oolitic rock tracts,as H uangjinkou (Xuanhan) Kaixian tract and Daxian Liangping tract,etc.Owing to the fact that the formation of the porous oolitic dolomites is related to the mixed water dolomization and deep seated solution,the reservoirs,as lenticular bodies with various sizes,are distributed in the dense oolitic limestones,making the ooliti c gas reservoirs having the property of lithologic structural combination trap. A s shown in the seismic sections,the reservoirs are of successive high amplitude reflection in the weak reflection background of the same horizon,because the sei smic mean velocity of the porous dolomite reservoirs is 5540 m/s and that of the dense limestones>6200 m/s.Therefore a comprehensive prediction based on the ide a of "Occupying edge,looking for bright spot and Coordinating structural trap" m ay be applied to prospecting for oolitic beach gas reservoirs.Except the wubaochang region,a key exploration tract,the Huangjin Kou(Xuanhan) Wanyuan and Dachuan Liangping regions are very hopeful explorati on reserve tracts and the Wanyuan Nanjiang region and Guangyuan Changpin region are the exploration potential ones.
In Dukouhe structure,etc.,some large and mediu m sized gas reservoirs which are composed of porous oolitic dolomites were foun d in Northeast Sichuan Basi n in the end of the 20th century,and the distribution of these reservoirs is rel ated to that of the oolitic beaches in Feixianguan Formation.Through research it is shown that the distribution of the oolitic beaches in Feixianguan Formation is controlled by the palaeogeographic pattern during Feixianguan Age,thus influe ncing the distribution of the oolitic beach reservoirs.The oolitic beaches in th e region are concentrically distributed along the carbonate platform edge of cir cum early Kaijiang Liangping trough.They were growing and moving along with th e enlargement of the carbonate platform sedimentation area and the elimination of the Kaijiang Liangping trough to form several developed oolitic rock tracts,as H uangjinkou (Xuanhan) Kaixian tract and Daxian Liangping tract,etc.Owing to the fact that the formation of the porous oolitic dolomites is related to the mixed water dolomization and deep seated solution,the reservoirs,as lenticular bodies with various sizes,are distributed in the dense oolitic limestones,making the ooliti c gas reservoirs having the property of lithologic structural combination trap. A s shown in the seismic sections,the reservoirs are of successive high amplitude reflection in the weak reflection background of the same horizon,because the sei smic mean velocity of the porous dolomite reservoirs is 5540 m/s and that of the dense limestones>6200 m/s.Therefore a comprehensive prediction based on the ide a of "Occupying edge,looking for bright spot and Coordinating structural trap" m ay be applied to prospecting for oolitic beach gas reservoirs.Except the wubaochang region,a key exploration tract,the Huangjin Kou(Xuanhan) Wanyuan and Dachuan Liangping regions are very hopeful explorati on reserve tracts and the Wanyuan Nanjiang region and Guangyuan Changpin region are the exploration potential ones.
引文
1 文应初,王一刚等.四川地区早三叠世飞仙关期碳酸盐岩台地增生与有利储集相带展布.天然气工业,1988;8(2)
2 罗志立.中国西南地区晚古生代以来地裂运动时石油等矿产形成的影响.四川地质学报,1981;3(1)
3 王一刚等.四川盆地上二叠统长兴组生物礁气藏形成机理.《海相油气地质》(’99海相碳酸盐岩与油气国际学术研讨会论文集),2000年第五卷第1～2期(总第17～18期)。
2 罗志立.中国西南地区晚古生代以来地裂运动时石油等矿产形成的影响.四川地质学报,1981;3(1)
3 王一刚等.四川盆地上二叠统长兴组生物礁气藏形成机理.《海相油气地质》(’99海相碳酸盐岩与油气国际学术研讨会论文集),2000年第五卷第1～2期(总第17～18期)。
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