物质平衡法计算地层剥蚀厚度——以南堡凹陷东营组为例

地层剥蚀厚度的恢复是盆地模拟中非常重要的一项工作,是反演盆地埋藏史和热史的前提条件。物质平衡法恢复地层剥蚀厚度是充分利用钻井、测井、地震等方法获得的地层物性资料来恢复地层剥蚀量的一种方法。该方法首先利用上下相邻地层的物性差别判断接触关系,在被剥蚀地层的顶部加入一厚度为H、岩性与残留部分相同的一段地层,使上下地层界面的物性差得到弥补,最后利用物质平衡原理得到初始沉积时的被剥蚀量。根据恢复地层剥蚀厚度的物质平衡计算模型编写计算机程序,使模型的计算更加准确、高效。基于物质平衡法模拟计算了南堡凹陷东营组地层的剥蚀厚度,计算出高35井、高62井、柳4井和柳13井东营组地层剥蚀厚度分别为486、466、573、634 m。模拟结果与前人研究成果对比表明,物质平衡法恢复地层剥蚀厚度是可行和有效的,与传统方法相比,物质平衡法所需要的物性资料较容易获取,适用于各个勘探阶段开展地层剥蚀量的研究。

EROSION THICKNESS RESTORATION BY MASS BALANCE METHOD: A CASE STUDY IN DONGYING FORMATION,NANPU SAG

The restoration of erosion strata thickness, as a precondition of burial history and thermal history inversion, is a very important work in basin simulation. Mass balance method is used to restore the strata erosion thickness through stratigraphic physical property obtained from drilling, well logging and seismic data. Firstly, the contact relationship of adjacent formations is judged by the physical property difference. A layer with a thickness of H and same lithology is put at the top of the eroding formation to balance the physical property difference. Therefore, the erosion strata thickness can be obtained by mass balance method. According to the computer program based on mass balance method, the calculation process of erosion strata thickness becomes more and more accurate and efficient. In this paper, according to mass balance method, the erosion strata thickness of Dongying Formation of Nanpu Sag has been calculated, which are 486m, 466m, 573m and 634m in Well G35, Well G62, Well L4 and Well L14 respectively. Simulation result indicates that it is feasible and effective to restore the erosion strata thickness using the mass balance method. Compared with traditional methods, the physical properties data needed by mass balance method are more accessible, so it is applicable to calculate the stratigraphic erosion amount in various exploration stages.