Numerical Study on the Prediction of “Sweet Spots” in a Low Efficiency-Tight Gas Sandstone Reservoir Based on a 3D Strain Energy Model

Abstract

The study of the construction of a micro-scale rupture parameter from the perspective of rock stress and strain is a frontier in geoscience. The strain energy density (U) can quantitatively characterize the probability of internal micro-scale ruptures in different types of rock. Based on this, in this paper, a systematic forecasting method for tight sandstone sweet spots in a low-amplitude tectonic zone based on U-value calculations was proposed. The specific steps are as follows. First, a geological model of the target layer was created, and a new rock mechanics parameter assignment method based on sedimentary facies control principle was proposed. Then, the palaeo-tectonic stress field of the target layer in the Yanshanian period was recovered through the boundary loading. Finally, the strain energy density distribution of the target layer was obtained based on energy conservation principle. The simulation results of the paleo-tectonic stress field show that, the distribution of horizontal stress is mainly affected by lithology and local structure, and the vertical stress is mainly affected by the burial depth. Stress diffusion occurs in some areas, which are mainly affected by lithologic mutations or complex structures. The U values of the target layers have a band-like distribution and are mainly distributed between 0.12 and 0.30 J•m −3. The relationship between strain energy density and productivity of tight sandstone reservoirs was analyzed, and the criteria for distinguishing sweet spot areas based on U values were proposed. This method is applicable to strongly heterogeneous tight sandstone reservoirs in the low-amplitude tectonic zone of the Ordos Basin and have reference values for similar types of reservoirs around the world. INDEX TERMS Tight gas sandstone, strain energy model, finite element method, tectonic stress field.

An improved method to characterize the pore-throat structures in tight sandstone reservoirs: Combined high-pressure and rate-controlled mercury injection techniques

“…With the increasing depletion of conventional oil and gas reservoirs, tight oil and gas reservoirs are becoming an area of increased research interest in the current geological community (Camp, 2011; Ghanizadeh et al., 2015a, 2015b; Yin and Gao, 2019). Recently, due to advances in microscale pore-throat characterization methods and horizontal drilling and hydraulic fracturing techniques (Benzagouta, 2015; Fall et al., 2015; Lu et al., 2015; Nelson, 2009; Rezaee et al., 2012), significant achievements have been obtained in the exploration and development of tight oil and gas reservoirs globally, such as the Cardium Formation in the Alberta Basin (Fic and Pedersen, 2013), the Barnett Formation in the Fort Worth Basin (Hill et al., 2007), and the Bakken Formation in the Williston Basin (Ghanizadeh et al., 2015a,b; Shen et al., 2018).…”

Tectonic evolution and gas control analysis of the Upper Palaeozoic tight sandstone reservoirs in the Linxing area of the eastern Ordos Basin

“…On the whole, the tectonic features of this area are complex. Clarifying the tectonic evolution and its gas control effect in this area has important guiding significance for specifying the direction of oil and gas exploration (Yin & Gao, 2019).…”

Characteristics, influencing factors, and prediction of fractures in weathered crust karst reservoirs: A case study of the Ordovician Majiagou Formation in the Daniudi Gas Field, Ordos Basin, China

“…The mechanical properties of rocks determine the type and degree of rock failure under the same tectonic stress environment, and can reveal the mechanical mechanism of rock ruptures (Atkinson & Meredith, 1987; Salamon, 1984; Yin & Gao, 2019; Zhao et al, 2017).…”