# A Study on the Remaining Reserves of the Weiyuan Shale Gas Block in Three-Dimensional Development
## 3 Evaluation of Remaining Reserves  
Three-dimensional development in multi-dimensional space is used to expand the coverage volume of the fracture network, transform the formation of artificial gas reservoirs, achieve the degree of utilization of reserves, and maximize the rate of return. In order to determine whether the Weiyuan block has the reserve potential and feasibility for three-dimensional development, its remaining reserves should be evaluated first. Petrel's functionality allows users to better understand the internal structure of reservoirs, more accurately define the spatial orientation of reservoir properties and measure reserve sizes and errors, easily utilize wellbore production information and numerical modeling information of reservoirs, and discover residual reserves and hidden reservoir recovery by selecting risk-based workovers and setting up wells and drilling trajectories, which, in turn, effectively reduces research and development (R&D) investment. The geological modeling is based on Schlumberger's Petrel software, which uses geometric analysis of the existing eight basic topological relationships to quantitatively characterize \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Evaluation Parameters**} & \multicolumn{3}{c}{**Classification of Reservoirs**} \\ \cline{2-4}  & **Class I** & **Class II** & **Class III** \\ \hline TOC (\%) & \(\geq\)3 & 2–3 & 1–2 \\ Effective porosity (\%) & \(\geq\)5 & 3–5 & 2–3 \\ Brittleness index (\%) & \(\geq\)55 & 45–55 & 30–45 \\ Total gas content (m\({}^{3}\)/t) & \(\geq\)3 & 2–3 & 1–2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Criteria for determining marine shale reservoirs of Wufeng–Longmaxi Formation. Figure 2: Reservoir division and development diagram. the internal structural features of the fault network. The stratification data of 17 vertical wells were used to analyze and fit the spatial heterogeneity of the reservoir; 23 logging data, permeability data, 56 gas saturation data, and 17 vertical wells were used to establish the attribute model. Finally, the model grid specification of the Weiyuan block was established as 1144 \(\times\) 393 \(\times\) 114, and the longitudinal grid spacing was mostly less than 1 m to reflect the change characteristics inside the storage unit, and a total of 51,253,488 (51.25 million) grid units were divided. Aiming at the situation that the geological modeling of shale gas reservoirs has many contents and complex relationships between the reservoirs, this modeling work mainly adopts the idea and technical process of level-by-level superposition modeling: 1 The shale gas reservoir tectonic model was established based on the data of drilling small layer division and comparison, and the results of tectonic fine interpretation of seismic data. 2 Based on the tectonic model, the matrix attribute model is established based on hard data from wells such as seismic sweet spot prediction results, sampled geologic experiment data, and logging interpretation results. 3 Based on the results of logging fracture interpretation, combined with the results of seismic fracture prediction, the fracture attribute model was established. 4 Based on the logging data, rock mechanics test and field geostress test data, the rock mechanics parameter model and geostress model were established to determine the spreading of the stress field under the complex geological structure. 5 The aforementioned models are fused and superimposed step by step to form a comprehensive geological model required for numerical simulation of shale gas reservoirs. 6 Calculation of shale gas geologic reserves based on a three-dimensional geologic model.