Horizontal Well Productivity Enhancement through Drawdown Management Approach in Vaca Muerta Shale

Abstract

Drawdown management optimization in overpressured formations is recognized as challenging by reservoir engineers. Well flowback operational procedures can vary widely and have an impact not only in the first months of production but on the long term performance as well. In this study, the results of choke management in more than a hundred horizontal wells in Loma Campana block, located in Vaca Muerta Shale Oil window, will be evaluated to investigate the potential impact on estimated ultimate recovery (EUR) and net present value (NPV). Using different flowback strategies, production data of wells in the same interval within Vaca Muerta Fm. have been analyzed using diagnostic plots commonly applied in unconventional reservoirs to identify early flow regimes. The evolution of stress over hydraulic fractures have been evaluated as well, which may contribute to a permanent conductivity loss due to hysteresis effects. Several forecasts have been created using Rate Transient Analysis (RTA) to quantify EUR loss due to aggressive choke management and to establish a relationship between drawdown and productivity degradation. The study found out that an aggressive choke management may cause a reduction in EUR of up to 20%. This can be attributed to a loss in fracture conductivity as a result of geomechanical-related factors. Therefore, an aggressive drawdown management is prone to minimize value, but understanding the tradeoff between the financial benefit due to production acceleration versus loss in reserves (as a result of fracture degradation) is the key issue that will be investigated in this paper. Furthermore, the proposed methodology used to integrate production performance analysis with the economic evaluation has allowed defining an optimum drawdown management for Vaca Muerta wells. Therefore, a standard procedure based on best practices is proposed for managing new wells put on production. As summary, this work provides evidence of production dependence on drawdown based on empirical data of horizontal wells in Loma Campana Oilfield. Complementing the study with RTA analysis has allowed quantifying the loss in EUR, estimating the effect of fracture degradation and verifying the economic impact. Finally, a workflow is proposed to accomplish optimum pressure decline with the right choke selection over time to optimize well performance.

Pressure Drawdown Management Strategies for Multifractured Horizontal Wells in Shale Gas Reservoirs: A Review

“…Rojas et al 67 developed RTA numerical simulators to perform history matching and production prediction on the production data of multiple shale gas wells and carried out an economic benefit evaluation to determine the optimal pressure drop scheme.…”

“…The cumulative production of gas wells with a high pressure control duration exceeds that of gas wells with a low pressure control duration, that is, productivity reversal occurs. 67 …”

“…The cumulative production of gas wells with a high pressure control duration exceeds that of gas wells with a low pressure control duration, that is, productivity reversal occurs. 67 According to the shape of the bottom hole pressure drop curve, the pressure drop path can be divided into linear decline, concave decline, convex decline, and stepwise decline. 60,110 Experimental results and numerical simulation analysis show that linear decline and stepwise decline can delay the permeability loss of reservoir seepage media compared with the depressurization production strategy and obtain a more ideal single-well production effect.…”

“…According to the decreasing speed of bottom hole flowing pressure, the pressure drop control strategy is divided into the conservative type, standard type, and aggressive type. ,, Studies have shown that there is an optimal pressure drop management time for bottom hole flowing pressure . Whether the pressure drops too fast or too slowly, the long-term EUR of the production well can be reduced.…”

“…When the initial reservoir pressure and final bottom hole pressure of the gas well keep constant, and the pressure control time increases, the average pressure drop rate of the gas well becomes smaller, and the initial production of the gas well gradually decreases. The cumulative production of gas wells with a high pressure control duration exceeds that of gas wells with a low pressure control duration, that is, productivity reversal occurs …”