Improved Oil Recovery (IOR) Method for Unconventional Reservoirs with a next Generation Huff-and-puff Treatment Combining Gas with Nanoparticles for Enhancing Recovery

摘要

Unconventional reservoirs unlocked through the combination of horizontal drilling and fracturing have revolutionized the exploration and production of hydrocarbons across the globe.For the United States,this success has opened the way to export these hydrocarbons,along with a new renaissance in the petrochemical processing industry,which is due to the supply of inexpensive energy and feedstocks.The Unconventional Revolution,now some 10+ years in the making,is still in its infancy.Next generation challenges for economic production include the need for improved hydrocarbon recovery.Current initial drilling and completion practices (aka primary recovery) only claim ~5-10% recovery of the oil in place.Initial decline rates for unconventional wells may vary between 75-95% in the first year alone.There is significant opportunity to improve upon secondary and tertiary recovery practices for unconventional reservoirs.One of the more recent methods of improved oil recovery (IOR) used on existing unconventional wells is combining two injectants,gases,and nanoparticles in a huff-and-puff (HNP) style treatment.Gases such as carbon dioxide (CO2) and nitrogen (N2) have a long history of use for improving recovery.Nanoparticles,a more recent innovation for recovery enhancement,initially demonstrated their ability for fracturing formulations in the field.Combining both gas and nanoparticles,in a traditional HNP-style injection in existing wells,creates a synergistic treatment that provides an improved incremental production of hydrocarbons over an extended period,thus providing a greater economic return for operators looking to enhance recovery from their existing wells.In our initial case study1,we treated a total of five open-hole completed horizontal wells in the Austin Chalk and Buda Limestone with a combination of N2 and nanoparticles.We monitored production for 180 days post treatment and reported on well response,showing incremental production improvements ranging from 12% to 564% BOE.With the key learnings from those first wells,we designed a treatment for the next well-a horizontal well in the EagleFord shale treated with nanoparticles and CO2,targeting production improvements that provide the operator payback within a 60-to 90-day period with incremental production lasting longer than six months.This new treatment method uses an HNP injection process,but injection period is typically a day or less and the recommended minimum soak period is normally 36-48 hours.This paper reports on the gas and nanoparticle HNP treatment positive response of EagleFord well's designed treatment and updates the continued production response of one of the initial five wells treated.What we have seen with the results to date is we can tune the right treatment combination,targeting a desired production response and economic return for the operator.This response may be measured as an increase in production and/or slowdown or retraction of the well's decline trend.