Study On Low-amplitude Structure & Horizontal Wells Evalution Of Ma5 Reservoir In Jianbian Gas Field

The Mawu segment of Majiagou formation in Ordovician is one of the favorable series of stratum in Jingbian gas field, Ordos basin. As the main reservoir Mawu13 layer in Mawu segment is depth, thin and strong heterogeneity and so on, vertical well developments have lower productivity. In order to improve the well production and recovery, the idea of using horizontal wells are proposed. However, low-amplitude structure in cross-well restricts capacity of horizontal wells on-site orientation in the process of design, deployment and implementation for horizontal well in Jingbian gas field. Based on the seismic explanation and logging and drilling data, the paper studies, describes and analyses the characteristic of low-amplitude structure, taking Shaan 190 and Shaan 200 well areas for example. This study arrives at the following conclusions in the hope of providing theoretical guidelines and development suggestions for the design and deployment and implementation of horizontal wells in Jingbian gas field.(1) Based on the fine subdivision and correlation of the Benxi Formation of Carboniferous and Mawu formation of Ordovician of 153 well, the 35 comparison sections and 35 gas reservoir profiles are mapped. Combined the study of horizon calibration, horizon track and time-depth conversion, the low-amplitude structures of reservoirs are mapped. Fold deformation in the study area is low amplitude and intermittent fold. Structural styles mainly include nose structure, dome and basin structure, but fold is very weak, mainly to nose structure and NE-NEE direction. It is stable craton block structural style.(2) The character of seismic wave for ancient valleys in different degree of erosion are forward modeling, includingâ‘ not eroded typeâ‘¡the concave typeâ‘¢concave-complex wave typeâ‘£onlap&erosional truncation type. These works provides an important theoretical guidance and reference for the identification of the ancient valleys. The two ancient valleys have developed in shan190 well area, which are the main NW-SE direction distribution rows. The six ancient valleys and some sub-ancient valleys have developed in shan200 well area, which are the main E-W direction distribution. The sub-ancient valleys are NE-SW or NW-SE direction distribution.(3) The methods of residual thickness and impression method are used to recover the paleogeomorphic features of the Ordovician. The paleokarst landform types are divided into 3 categories, including karst platform, karst slope and karst valleys. The karst valleys play an important role in controlling the degree of natural gas enrichment of the Mawu segment.(4) Based on the comprehensive analysis of the low-amplitude structure, the combination types of nose structure are summed up 5 categories. Traps are divided into 2 categories and 7 sub-categories after the study with the relationships between gas enrichment and structure, formation, karst topography. The combination trap with ancient landform-formation-structure is the mainly type of natural gas enrichment. The favorable structure of side of ancient valleys provides geology evidence for arrangement well in the future.(5) The correlation coefficients of the relationship between horizontal section drilling track of the two high-yielding horizontal wells and the low-amplitude structure for objective layer are better, because R2 are 0.6548 and 0.8647.(6) Based on the comprehensive analysis of the relationships of between gas enrichment and low-amplitude structure, ordovician paleokarst landform, ancient valleys, thickness of Mawu1+2, and thickness of Mawu13 as main gas layer,14 favorable targets are recommended.