Seismic EOR—The Optimization of Aging Waterflood Reservoirs

Abstract

The majority of enhanced oil recovery projects currently underway are based on Water floods which are known to provide lesser recovery compared to other recovery mechanisms. Many such reservoirs exist where the recovery has been less than 30% altogether due to various drawbacks of the conventional Water floods. The paper would like to discuss a new EOR technique using Acoustic and Seismic energy to reduce interfacial tension and promote coalescence of oil ganglia using the resonant frequency principle. The technique uses pressure and sound waves at pre-determined frequencies to set the oil molecules in motion to promote coalescence and thus reducing the fingering effects. The flood pattern can be optimized by recovering oil from previously unswept areas. It thus enhances the life of the primary flood providing valuable economic savings. The process can also be applied to various reservoirs in their tertiary recovery phase to extend the life of the project. Experiments conducted in the lab show that the frequency of oil and water may differ from reservoir to reservoir and compositional analysis of samples is required to determine the resonating frequency. The design of the downhole tools for injector wells to implement this technique are also discussed briefly. Introduction The Oil production is on decline with all major producing reservoirs already reaching their peak period, thus emphasizing the need of enhanced oil recovery techniques to produce oil left in the reservoir after waterflood and other pressure maintenance techniques. According U.S. Department of Energy, more than 60 % of the oil is left in the reservoirs which are currently the target for EOR. Various methods have been proposed and many have been implemented in fields around the globe. They include chemical, thermal, microbial and many others. They all aim to reduce the residual oil saturation in the reservoirs to increase Expected Ultimate Recovery (EUR) and Recovery Factor. Seismic stimulation is also one of the techniques which follow the underlying principle of reduction of residual oil saturation. The interest in Seismic or Vibrational stimulation is a few decades old, primarily with research projects being carried out in the 50's in the United States and Russia where effect of earthquakes and Human induced shocks on oil production was studied and various reports were published postulating the underlying principle for the process.

Modified model of porosity variation in seepage fluid-saturated porous media under elastic wave

“…Low-frequency vibration production technology could improve the oil recovery through the follow mechanisms (Cidoncha 2007;Ariadji 2005;Kurawle et al 2009): (1) reducing the capillary forces and fine particles blocking rate inner pore throats could increase the absolute permeability of rocks; (2) crude oil viscosity decrease, hydrophilicity increase on rock surface, and an additional drive force added by vibration could improve the fluid seepage rate; (3) velocity difference between solid and fluid might increase crude oil detachment or extraction in bypassed throats, so as to reduce residual oil saturation and improve oil recovery. Thereby, the real pore volume under wave is only part of the whole pores.…”

An extended model for ultrasonic-based enhanced oil recovery with experimental validation

“…In summary, from these studies, it has been concluded that ultrasonic-based EOR can be applied to any type of oil reservoir and may also be useful in heterogeneous environment [21][22][23]. However, to our knowledge, no literature has addressed simultaneously both the experimental and simulation studies with a detailed mathematical modeling.…”

Conventional versus electrical enhanced oil recovery: a review

“…Many field tests have also been performed with the application of ultrasonic waves to oil fields resulting in . From these studies, it has been concluded that ultrasonic-based EOR can be applied to any type of reservoir and may also be useful in heterogeneous environment (Chen and Fairbanks 1969;Amro and Al-Homadhi 2006;Kurawle and Kaul 2009). According to some authors, small oil droplets, which usually are found in the reservoir after primary recovery, may coalesce to form larger ones leading to the flow of oil which results in oil recovery (Beckham 2009;Jeong et al 2011).…”

“…Experiments have also been conducted to verify that ultrasonic waves have no effect on rheology of crude oil with different asphaltene levels proving that they can be suitably used for EOR (Gizem Gunal and Islam 2000). From these studies, it has been concluded that ultrasonic-based EOR can be applied to any type of reservoir and may also be useful in heterogeneous environment (Chen and Fairbanks 1969;Amro and Al-Homadhi 2006;Kurawle and Kaul 2009).…”