Sensitivity analysis study on the parameters affecting the performance of hydraulically fractured wells in tight oil reservoirs

Abstract Over the last 20 years, tight oil reservoirs have significantly impacted the oil industry as one of the important unconventional oil resources. However, their development is so costly and complicated because it requires drilling very long horizontal wells and performing many stages of hydraulic fracturing. To optimize the production process in tight reservoirs, the parameters affecting the performance of hydraulically fractured wells in such reservoirs should be determined and statistically ranked in terms of their importance. Therefore, identifying the parameters that most strongly control well performance is essential for efficient development and hydraulic fracture design. In this study, the sensitivity analysis approaches were applied on tens of tight oil reservoir models by using two statistical methods. The first method was one parameter-at-a-time (OAT), in which each parameter was varied while the others were kept constant. The second was the design of experiments (DOE), in which the investigated parameters were varied simultaneously to quantify their relative effects. The investigated parameters in this study were the horizontal permeability, vertical permeability, porosity, half-length of hydraulic fractures, fracture permeability, rock compressibility, and the hydraulic fracture thickness. The novelty of this study lies in the combined use of OAT and DOE to quantitatively rank the effects of reservoir and hydraulic-fracture parameters within a consistent simulation framework. The results of OAT indicated that the horizontal permeability of the matrix is the most important factor on the objective functions which are the oil rate and the Cumulative oil production; however, the fracture permeability is with the least effect. The results of the DOE are consistent with the outcomes of OAT where we noticed that the highest effective parameter is the horizontal permeability, as its effect on the accumulated oil reached a percentage of 62%. According to the sensitivity analysis, increasing the hydraulic-fracture half-length to 90 m increased the oil rate to approximately 53.8 m 3 /day and the cumulative oil production to 29,843.88 m 3 in the investigated model, indicating its potential to improve oil recovery.