陆相湖盆块体搬运体的沉积特征、识别标志与形成机制

块体搬运体已经成为大陆边缘重力流勘探的新领域。与大陆边缘相比,陆相湖盆是否存在大规模的块体搬运体及其沉积特征、识别标志、形成机制、分布规模、外部形态及与浊积岩的差异性都是值得探索的重要课题。利用松辽和二连等坳陷或断陷盆地的地震及岩心、分析化验资料,对上述问题进行了探讨和研究。陆相湖盆的重力流可以分为块体搬运体和浊积岩,二者在沉积特征、流体浓度、流态、流变学特征及地震响应特征等方面都存在显著差异。块体搬运体以层流为主,具有固体和宾汉流体的特征,常见弹性、脆性及塑性形变,除常见块状砂岩外,还发育大量包卷层理、滑塌变形构造、布丁构造及微断裂等同沉积或软沉积变形构造,同时也可见到泥岩漂砾等;浊积岩以紊流为主,具有牛顿流体的特征,发育递变层理。厚层块体搬运体在地震上具有透明和乱岗状的弱反射特征,而薄层块体搬运体具有眼球形的强反射结构。块体流不仅具有重力流的粒度分布特征,同时还具有牵引流的粒度分布特征。与浊积岩相比,块体搬运体在陆相湖盆的分布更为广泛,不仅层数多,而且单层厚度大,具有更好的储集性能,是中国陆相湖盆重力流勘探的新领域。

Deposition characteristics, recognition mark and form mechanism of mass transport deposits in terrestrial lake Basin

Extensive mass transport deposits （MTDs） distributed in continental margin have became new filed of gravity flow exploration and development. In order to understand the sedimentary and distribution characteristics of the MTDs which deposited in depression and faulted basins, Songliao Basin and Erlian Bain are chosen as the research object. Based on integrated analysis of seismic, core and laboratory test data, sedimentary features and distribution pattern of MTDs were studied systematically. Gravity flow deposits can be divided into MTDs and turbidite. MTDs are different from turbidities in terms of sedimentary structure, concentration, flow pattern, rheology characteristics and seismic response. MTDs belong to laminar flow with solid and bingham fluid characteristics simultaneously and include movement andemplacement by elastic deformation and brittle deformation and plastic deformation. Besides the common massive sandstone, MTDs also form synsedimentary deformation structures or soft-sedimentary deformation structures, such as convolute bedding, slumping deformation structure, boudinage and microfaults, as well as shale boulder. Turbidite belongs to turbulence which forms grained beddings. Seismic profile reveals that thick layer of MTDs are characterized by chaotic, mounded, and transparent seismic reflection, and thin layer of MTDs have eye-shaped reflection structure. MTDs not only have the particle size distribution characteristics of gravity flow, but also have the particle size distribution characteristics of traction current. MTDs are more widely distributed than turbidite in the study area, have more layers and larger monolayer thickness, and have better reservoir performance. The study shows that MTDs are new areas for terrestrial lacustrine gravity flow exploration.