A Semi-Analytical Model Based on the Volumetric Source Method to Predict Acid Injection Profiles of Horizontal Wells in Carbonate Reservoirs

Abstract

Acid treatment is an important measure to improve production for horizontal wells of carbonate reservoirs. Acid injection profile of horizontal wells (AIPHW) is the most critical indicator of the success of the acidification. Currently, most previous works study AIPHW based on the point source method. However, an inherent singularity exists in the point source solution, which leads to the calculation speed is too slow or the solution does not converge. To solve this problem, a semi-analytical model (coupling the wellbore flow model and reservoir seepage model) by the volumetric source method is presented to determine AIPHW in carbonate reservoirs. In this new coupled model, the permeability heterogeneity, formation contamination, acid-induced wormhole formation and wellbore pressure drop are all considered. The results of the validations show that the results from the proposed method match well with the model results from the literature. Then, the effects of the acid injection flow rate, acid injection time and permeability heterogeneity on the AIPHW are studied. According to the sensitivity analysis, we find that the disequilibrium degree of AIPHW become stronger as acid injection flow rate increase, acid injection time goes on, and permeability heterogeneity coefficient increase. This study provides an instruction for the design of horizontal well acidification and the evaluation of acid treatments of horizontal wells in carbonate reservoirs.

Semi-Analytical Model Based on the Volumetric Source Method to Production Simulation from Nonplanar Fracture Geometry in Tight Oil Reservoirs

“…Based on the assumptions, only a single-phase oil exists in the tight oil reservoir. Because point source functions also have the disadvantage that their solution has a singular point, − we applied the volume source function proposed by Valko and Amini . As shown in Figure , the single-phase fluid flow from reservoir to fracture in the tight oil reservoir system can be described by the diffusion equation with volumetric source …”

“…In previous studies, researchers have built semi-analytical models based on the point source function for predicting the production of fractured wells. − However, point source functionality has a disadvantage: its solution has a singular point because the source of the model has no volume. − To deal with this issue, the volumetric source function was proposed by Valko and Amini; this function has higher computational efficiency and accuracy than the point source function. Furthermore, a series of production prediction models for fractured wells were built by the volumetric source function. − …”

Simulation of reservoir dynamic damage and influencing factors of horizontal wells in heterogeneous carbonate reservoirs

“…The damage to the reservoir in horizontal wells is intricately linked to the stimulation technology utilized. A comprehensive comprehension of the reservoir damage, particularly the distinct uneven distribution of the affected zones along the horizontal wellbore, can effectively aid in the selection of the appropriate acidification method and refine the acid distribution process, ultimately enhancing the effectiveness of plug removal 5–9 …”

“…A comprehensive comprehension of the reservoir damage, particularly the distinct uneven distribution of the affected zones along the horizontal wellbore, can effectively aid in the selection of the appropriate acidification method and refine the acid distribution process, ultimately enhancing the effectiveness of plug removal. [5][6][7][8][9] Compared to vertical wells, horizontal wells have a larger contact area with the reservoir, and the duration of contact between the drilling fluid, completion fluid, and the reservoir is significantly longer. The pressure difference when drilling into oil and gas reservoirs is greater than that of vertical wells.…”

Effect of Sulfur Deposition on the Horizontal Well Inflow Profile in the Heterogeneous Sulfur Gas Reservoir

“…Souza et al proposed a numerical model to simulate the coupling of the wellbore and reservoir, which takes into account factors such as wellbore length, isotropy and anisotropy, completion scheme, and formation damage near the wellbore area. However, this method needs longer computational time than the analytical method and semianalytical method. − The volumetric source method was proposed to evaluate the inflow profile for horizontal well completion with inflow control devices, and computational efficiency and high accuracy were obtained. The reservoir/well model of Furui was improved by Adesina et al, who considered the pressure drop caused by acceleration.…”