A novel approach to the comprehensive evaluation of geology- engineering dual sweet spots in tight gas reservoirs in the LX area of China

Abstract

The LX tight gas reservoir displays significant heterogeneity, with a lack of alignment between engineering treatment and geological evaluation, leading to an unsatisfactory development outcome. Focusing on the Shihezi Formation of LX, a new comprehensive evaluation method is proposed for identifying sweet spots, taking into consideration both geological and engineering factors. The objective function utilized is post-frac production, and the grey correlation method was employed to quantitatively characterize the weight coefficients of geological and engineering parameters. The dual sweet spots index F was obtained through a normalized process. Utilizing the Petrel integrated exploration and development platform, the dual sweet spots index was incorporated into the geological model using coarse-interpolation. Subsequently, a dual sweet spots evaluation model was established to enhance the overall assessment process. The findings indicate the following: (1) There is a strong correlation between open flow production and the F-value, and the model's predicted value closely aligns with the actual value. (2) A section with an F-value greater than 0.5 is identified as the optimal sweet spot, prioritizing development in this area. Sections with F-values within the range of 0.3 to 0.5 may be considered for fracturing but are not the primary choice. Sections with an F-value below 0.3 are deemed inefficient areas. (3) Based on the dual sweet spots evaluation model, it is recommended to focus on single layers He2, He5, and He6 in the LX area due to their superior quality compared to other layers. The research results offer crucial technical support for assessing fracability in this region, and hold significant importance for the selection of fracturing wells and the optimization of frac design.