元素录井技术在海陆过渡相页岩气水平井地质导向中的应用

河南省页岩气资源主要发育于上古生界海陆过渡相沉积中,海陆过渡相页岩气层系具有多岩性频繁互层、单层厚度小、纵向变化快的特点,加上局部地区微幅构造发育,使得水平井地质导向中小层识别和水平段钻头方向的判断难度很大。为此,利用研究区优质页岩气层段的X射线荧光元素录井数据,通过统计分析对目的层各小层进行精细刻画,首次提出利用Si、Al、Na、Fe、S、K、Mn和Ti元素含量的变化关系分别建立砂岩、煤岩和泥岩元素交会图版,并利用Ba、Ti、Ca、S和Sr元素组合与深度的关系建立随钻元素定量模型。根据元素交会图版进行目的层小层识别,为水平井入窗提供准确依据;在水平段利用随钻元素定量模型判断钻头穿行方向。该技术在通许隆起中部中深层页岩气水平井钻井过程中进行了现场应用,取得了较好的效果。

Application of element logging in horizontal well geosteering of marine-continental transitional shale gas

In Henan Province, shale gas is most enriched in marine-continental transitional sediments, which have the characteristics of frequent interbedded lithology, small thickness of single layer and rapid change of longitudinal lithology. Due to the Sedimentary characteristics and micro-structures developed in some areas, it is very difficult to identify the thin layers and determine the bit direction. To solve this problem, the element logging data of quality shale gas layers in study area was used for fine characterization of target thin layers by means of statistical analysis. This paper put forward a method to establish element intersection charts of mudstone, sandstone and coal by virtue of the relationship change among 8 element contents ( Si, Al, Na, Fe, S, K, Mn and Ti), as well as a quantitative model while drilling depending on the relationship of depth and element combination ( Ba, Ti, Ca, and Sr). The element intersection charts was used to identify target thin layers, in order to provide the accurate basis for window-entering of horizontal well; and the quantitative model while drilling was used to determine the bit direction. The application of element logging technology in one horizontal shale gas well in central Tongxu Uplift has achieved remarkable results.