The Key Technique Research and Application of “Sweet Spots” Prediction in the Xihu Depression of Low Permeability and Porosity Reservoir: A case study from the Huangyan-A Gas Field

Key words: 
• low permeability /
• geophysical characteristics /
• pre-stack synchronous inversion /
• reservoir reconstruction /
• "

Abstract: Xihu sag has the characteristics of deep burial depth, low porosity and permeability, Reservoir cannot be produced at economic flow rates without assistance from reservoir reconstruction, and the prediction of "sweet spot" reservoir distribution is the important process of reservoir reconstruction. The elastic parameter which is sensitive to "sweet spot" can be found by petro-physics analysis, and its threshold value can also be set. The characteristic of seismic reflection for "sweet spot" is analyzed by seismic forward modeling, and the feasibility of porosity and gas bearing prediction can also be analyzed. The accurate parameter is predicted by pre-stack synchronous inversion with the constraint of AVO parameter, and then it describes the distribution characteristic of sand thickness, strata slices, porosity, gas bearing and brittleness index. According to the lower limit of "sweet spot" in the study area, the favorable area of each attribute is delineated, and the favorable zone of "sweet spot" reservoir in study area is obtained, which gives a base for the well location design of horizontal multi-stage fracturing. The prediction result is verified by drilling, furthermore, it has achieved "double hundred" rate of sand and gas drilling encountered in target layer.