Parameters Affecting Load Recovery and Oil Breakthrough Time after Hydraulic Fracturing in Tight Oil Wells

Abstract

After hydraulic fracture treatment, wells typically produce significant volumes of water, which is primarily recovered fracturing fluid. The amount of fracturing fluid produced back is called load recovery. Single phase water production may continue for several days before oil breakthrough from the formation occurs. A wide range of load recoveries (15%–80%) are reported in the literature, depending on various reservoir, fracture, pumping and operational parameters. This study conducts a comprehensive numerical and statistical analysis to identify the most important parameters affecting load recovery. The sensitivity of oil breakthrough time to these parameters is also investigated. A fit-for-purpose model was created using a commercial coupled reservoir flow/geomechanics simulator to simulate fracturing treatment and flowback operations. Water and oil production trends, and flow regimes observed in the model, are verified using rate-transient analysis (RTA). The effect of twenty parameters including pumping rate, shut-in time, producing bottomhole pressure, production rate constraint, matrix porosity and permeability, matrix and hydraulic fracture compressibility, relative permeability end points and capillary pressure on load recovery and oil breakthrough time is investigated by utilizing Design of Experiment (DOE). The developed model considers non-uniform leak-off during pumping, providing a better understating of water retention, while the application of the DOE method allows the effect of various parameters and their interaction to be studied rigorously. A critical finding is that the majority of total load recovery occurs within the first three months of production. Furthermore, matrix permeability, shut-in time, connate water saturation and fracture compressibility, were found to be the most dominant factors, which can impact the load recovery by up to 22%, 15%, 14%, and 13%, respectively. Matrix permeability, production rate constraint, fracture residual oil saturation and shut-in time are four of the prominent parameters affecting oil breakthrough time. Understanding the impact of operational parameters such as shut-in time and production rate can help industry to implement recycling/disposal options and ultimately optimize load recovery. This can also create significant environmental compliance benefits for operators in addition to benefitting operational efficiency.

Numerical Investigation of Fracture Compressibility and Uncertainty on Water-Loss and Production Performance in Tight Oil Reservoirs

“…Therefore, a series of models were established to quantify the impact of various factors on water-loss and production performance. The flow regimes observed in Figure 9 are consistent with field observations and analytical models for flowback analysis [61][62][63]. The first two flow regimes are well captured and last for more than two days.…”

“…This transition might be very short depending on the fracture conductivity and fracture complexity; and, finally, (4) matrix boundary dominated flow (unit slope) occurs when the density of natural fractures is large and the spacing between hydraulic fractures is small, the pressure response quickly propagates to the matrix boundary. The flow regimes observed in Figure 9 are consistent with field observations and analytical models for flowback analysis [61][62][63]. The first two flow regimes are well captured and last for more than two days.…”

Contaminación físico química en zonas de fracking

“…Aunque recientemente la técnica ha variado en cuanto a la composición del líquido inyectado, sus componentes no se conocen en su totalidad [17] ya que no están en el dominio público por considerase secreto industrial. Se conoce que el líquido de reflujo y el producido se reutilizan parcialmente en la técnica de fracking [18].…”

A Comprehensive Model for Estimating Stimulated Reservoir Volume Based on Flowback Data in Shale Gas Reservoirs

“…Due to the ultralow permeability of shales (from 10 −23 to 10 −17 m 2 ) [3], a combination of horizontal drilling and multistage hydraulic fracturing has been widely used to SRV, which increases effective contact significantly to improve gas production from an individual well. Therefore, characterization of the stimulated reservoir volume appears to be of vital importance to manage and predict shale reservoir performance [4,5].…”