薄互层型沉积体储层构型建模

Modeling of the Reservoir Architecture of Thin Interbedded Deposits

牟中海 刘雪 常琳 苏秋 吴千然

MOUZhonghai LIUXue CHANGLin SUQiu WUQianran

西南石油大学地球科学与技术学院, 四川 成都 610500 中国石油青海油田分公司, 甘肃 敦煌 736202 中国石油塔里木油田分公司勘探开发研究院, 新疆 库尔勒 841000

Southwest Petroleum University, School of Geoscience and Technology, Chengdu, Sichuan 610500, China Qinghai Oilfield Company, PetroChina, Dunhuang, Gansu 736202, China Exploration and Development Research Institute, Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China

以柴达木盆地昆北油田切六区辫状河三角洲为例，探讨了薄互层型储集砂体构型的建模方法。采用基于半幅点小层划分原则进行小层划分，克服了传统的基于自然伽马相对极大值和（或）自然电位正异常来确定小层界线而无法获得真正的储层、隔层厚度与深度的缺陷。分析了研究区夹层类型与分布，认为研究区以泥岩夹层为主，夹层的分布以局部为主，在此基础上，用低渗层厚度和渗透率回返程度两个参数来识别夹层，从而可以大大提高建模精度。依据辫状河三角洲受河流、湖浪双重水动力控制，地层具低倾角砂泥岩薄互层的特点，提出了"硬"数据控制、分层建模、储层与夹层钳套的薄互层型沉积体构型建模研究思路，建立了昆北地区切六区辫状河三角洲构型模型。通过对构型模型进行构型单元间关系的研究认为，目的层存在侧向拼接、侧向分隔、进积型、加积型4种构型模式，但以各种砂体的横向拼接与纵向加积模式最为发育。与传统建模方法比较，在薄互层沉积的情况下，新建模方法更具优势和合理性。

Taking the braided river deltas of the Q6 Block in the Kunbei Oilfield in the Qaidam Basin as an example, this study investigated methods to model the architecture of thin interbedded reservoir sandstones. Traditional methods are based on the relatively maximum values of natural gamma measurements and (or) positive spontaneous potential abnormalities to determine the boundaries of sub-layers. Meanwhile, the sub-layer division based on the tangent points of reflected and diffracted wavefronts can more accurately depict the thickness and depth of reservoir layers, insulating layers, and interlayers. The interlayers in the study area are dominated by localized mudstones. Hence, two parameters, the thickness of low-permeability layers and permeability return level, were adopted to identify the interlayers. This enhanced the model accuracy. Because the braided river deltas were under the hydrodynamic control of both river and lake waves and the strata are characterized by thin interbedded low-inclination sand-mudstones, this study proposes that strict data control, hierarchical modeling and reservoir layer/interlayer nesting should be included to construct an architectural model of the thin interbedded deposits. Subsequently, an architectural model for the braided river deltas of the Q6 Block in the Kunbei region was established. Analysis of the relationships between the architectural units of the model shows that there are four types of architecture in the target layers. They are lateral stitching, lateral separation, progradation, and accretion. Among them, the lateral stitching and vertical accretion modes of the sand bodies are the most developed. Compared to the traditional modeling method, the proposed method is more advantageous and sensible for thin interbedded deposits.

10.11885/j.issn.1674-5086.2018.11.21.06