通南巴地区膏盐层分布及其流变学特征

Distribution and rheological characteristics of evaporates in Tongnanba area

通南巴地区膏盐层层位稳定,形态分布一般平稳连续;当上、下能干层(白云岩层)受到褶皱及断层影响发生形变时,膏盐层呈丘状、楔状、纺锤状等异常膏盐体形态。膏盐层具有多层分布(57～110层)、累计厚度大(273～415 m)的特征,其空间展布与上、下能干层的形态和构造特征关系密切:①白云岩岩层的初始主波长大于膏盐层厚度,能干层间及其所夹膏盐层互相影响,膏盐层变形受接触应变带影响较大,易于形成不协调褶皱;②受应力、温度、流体等因素影响,膏盐岩容易发生蠕变断裂,并在上、下能干层断裂的触发下,发生蠕变流动,形成异常膏盐体。多层分布的膏盐层其封闭能力较单一、巨厚膏盐层的封闭能力弱;异常膏盐体的厚度显著增大,其周围可能是油气勘探的有利场所。

The vertical distribution and geometry of evaporates in Tongnanba area are generally steady and continuous. However,when the overlying and underlying competent dolomite are deformed by folds and faults, they occur in special shapes like moundy,wedge and spindle set. The evaporates are characterized by multilayers （57 - 110 ） , a large gross thickness （273-415m） ,and close relationship with the shapes and structures of competent beds. The initial dominant wavelengths of the dolomite layers are larger than the thickness of evaporates, the evaporates and the surrounding multiple competent beds interact with each other, and the contact strain zones have relatively large influences on the evaporates, therefore, the evaporates are apt to form disharmonious folds. The evaporates are easy to form creep fractures due to the influences of stress, temperature, fluid and other factors, and abnormally-shaped evaporate bodies are developed due to faulting of the competent beds. It was proved that sealing capability of muhilayer evaporates was weaker than that of single evaporates with large thickness. The thickness of evaporate body enlarges significantly when they get abnormally-shaped, thus the surrounding areas are favorable targets for hydrocarbon exploration.