The oil-based drill solids are regarded as controlled or hazardous waste since it is contaminated with oil and other organic/inorganic contaminants. As such, the drill solids can be disposed with 3 different ways: (1) decontamination treatment before discharged into the sea; (2) re-injecting the drill solids into the well or (3) hazardous waste controlled landfill. The disposal of the drill solids in the landfills is usually the last environmental option. The lowest environmental impact way for the solid disposal, especially for offshore operation, is still a decontamination treatment before discharged. However, the conventional decontamination technology still exhibits limited efficiency to extract oil from the drill solids; yielding the oil content in the treated solids of much greater than 1% oil content in the dried solids, which does not meet a strict environmental regulation in many highly ecological-sensitive countries (e.g. UK and North Sea countries, etc.).
This paper demonstrates a new promising technology to overcome this efficiency limitation, called nanoemulsion. Nanoemulsion is a water-in-oil emulsion, having the Winsor type III or IV stages but with high surfactants-to-interface ratio. When analyze using dynamic light scattering, it shows the natural distribution of <100nm particle size. Nanoemulsion is able to provide ultralow interfacial tension (IFT) of <0.01mN/m. According to Laplace Pressure equation, when IFT is extremely low, less energy is required to remove the oil that trapped inside the pores. Recently Nanoemulsion has been demonstrated able to remove sticky oil-base mud inside the wellbore and able to suspend the mud after treatment. When using it to remove the oil from the drill solids, it is able to reduce the contact angle and capillary force on the solid particle surface, subsequently, allowed water to penetrate and wet the particle surface and accessible pores. This mechanism indeed converts the surfaces become water-wet (hydrophilic). Once the particles surfaces are water-wet, oil will instantly desorb from it and easily segregate through centrifuge force. Different proposed process will be shared and discussed in this work. It was found that the oil content in the drill solids after treatment with nanoemulsion cleaning process was able to reach <1%.
Ji, Lujun (M-I Swaco) | Guo, Quan (M-I Swaco) | Friedheim, James E. (M-I Swaco) | Zhang, Rui (China University of Petroleum Huadong) | Chenevert, Martin E. (University of Texas At Austin) | Sharma, Mukul Mani (University of Texas At Austin)
Although key shale gas plays vary considerably in terms of reservoir pressure, temperature, mineralogy, and in-situ stresses, the principal drilling-related issues are wellbore stability, shale inhibition, hole cleaning and rate of penetration. Because many of the shale reservoirs are in either environmentally sensitive or densely populated areas, stricter environmental regulations will require new types of environment-friendly water-based drilling fluids. The traditional shale inhibition method through either chemical inhibition or use of invert emulsion drilling fluid is not enough to satisfy the stricter environmental requirements.
This paper focuses on the lab techniques and the performance results of evaluating and analyzing an innovative water-based drilling fluid system containing nanoparticles as a physical shale inhibitor. The physical shale inhibition is achieved by plugging the pores and microfractures in shale with nanoparticles and thus preventing water invasion into the shale. A series of transient pressure penetration or flow-through tests, also known as shale membrane efficiency tests, were performed to evaluate water invasion rates into various shale core samples, with initial brine permeabilities varying from less than 1 nD to over 100,000 nD. Permeability reduction was used as a proxy of water invasion reduction and the effectiveness of plugging of pores and microfractures in shale by the nanoparticles. Many orders of permeability reduction were consistently observed for the drilling fluids with nanoparticles.
Pressure increases in the near-wellbore region due to water invasion during a given time also were analytically calculated using the permeabilities for various fluids which were interpreted from these transient flow-through tests. These pressure increases then were compared to illustrate the approximate impact depth of water invasion and give an indication of shale stability and shale inhibition performance of these drilling fluid systems.
Test results and pressure increase analyses showed that this new water-based drilling fluid with nanoparticles provides an entirely different type of shale inhibition by physically plugging pores and microfractures in shale and meets the strictest environmental regulations for shale gas drilling. The tests also showed that although nanoparticles alone may be effective in preventing water invasion into shale samples with no microfractures, the combination of properly formulated drilling fluid and nanoparticles of appropriate size and concentration is the key to prevent water invasion into shale gas core samples with or without microfractures.
Depletion of many conventional oil and gas reserves and increasing energy demand have heightened the importance of developing techniques to effectively and efficiently drill gas/oil shale. Traditionally, shale is considered as hydrocarbon source rock and/or seal rock only; some shale plays are now recognized as major unconventional hydrocarbon reservoirs. Worldwide, likely recoverable shale gas reserves exceed 250 Tcf by some estimates, with over 10 times that speculated to be in place. In North America, shale gas has been one of the most rapidly expanding trends in onshore domestic natural gas exploration and exploitation (Sandrea 2006).
Fakhimi, A. (Department of Mineral Engineering, New Mexico Institute of Mining and Technology and Department of Civil and Environmental Engineering, Tarbiat Modares University) | Nunoo, S. (Department of Mineral Engineering, New Mexico Institute of Mining and Technology, and School of Engineering, University of British Columbia) | Van Zyl, D. (Department of Mining Engineering, University of British Colombia) | McLemore, V.T. (New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology)
Zhou, Y. (University of Pittsburgh) | Zhang, W. (National Energy Technology Laboratory) | Gamwo, I.K. (National Energy Technology Laboratory) | Lin, J.S. (National Energy Technology Laboratory, University of Pittsburgh) | Eastman, Harvey (National Energy Technology Laboratory, URS Corporation, National Energy Technology Laboratory) | Whipple, Gordon (National Energy Technology Laboratory, URS Corporation, National Energy Technology Laboratory) | Gill, Magdalena (National Energy Technology Laboratory, URS Corporation, National Energy Technology Laboratory, West Virginia University)
New technologies are emerging oil industry to afford the need for increasing oil recovery from oilfields, one of which is Nanotechnology. This paper experimentally investigates a special type of Nanoparticles named Polysilicon ones which are very promising materials to be used in near future for enhanced oil recovery. There are three types of Polysilicon Nanoparticles which can be used according the reservoir wettability conditions. In this paper, hydrophobic and lipophilic polysilicon (HLP) and naturally wet polysilicon (NWP) are investigated as EOR agents in water-wet sandstone rocks. These two Nanoparticles recover additional oil through major mechanisms of interfacial tension reduction and wettability alteration. The impact of these two Nanoparticle types on water-oil interfacial tension and the contact angle developed between oil and the rock surface in presence of water phase were investigated. Then, several coreflood experiments were conducted to study their impacts directly on recoveries. Furthermore, optimum pore-volume injection of each Nano-fluid was determined according the pressure drop across the core samples.
The results show a change toward less water-wet condition and a drastic decrease in oil-water interfacial tension from 26.3 mN/m to 1.75 mN/m and 2.55 mN/m after application of HLP and NWP Nano-fluids respectively. As a result, oil recoveries increase by 32.2% and 28.57% when a 4 gr/lit concentration of HLP and NWP Nano fluids are injected into the core samples respectively. According the differential pressure data, two and three pore-volume injections of NWP and HLP Nano-fluids are the best injection volumes respectively. Finally, HLP and NWP Nanoparticles improve oil recovery without inducing any formation damage according the oil recovery and pressure drop data.
To meet the rising energy consumption in the world, there is a dire need to produce more crude oil. Stagnant oil production and unimpressive recovery by primary and secondary recovery methods have made the situation more precarious. Hence, attention is being paid to more efficient technology (i.e. Nanotechnology) for recovering more oil from the existing oilfields. On an average, only about a third of the original oil in place can be recovered by the primary and secondary recovery processes (Kong and Ohadi, 2010). The rest of oil is trapped in reservoir pores due to surface and interfacial forces. This trapped oil can be recovered by reducing the capillary forces that prevent oil from flowing within the pores of reservoir rock and into the well bore (Wu et al., 2008). Capillary pressure which is the force necessary to squeeze a hydrocarbon droplet through a pore throat (Bear, 1988) reduces by reduction of oil-water interfacial tension and wettability alteration. Polysilicon Nanoparticles have a great potential for increasing pore scale displacement efficiency through reduction of interfacial tension and wettability alteration. There exist three types of polysilicon Nanoparticles, which can be used in proportion to reservoir wettability (Ju, 2002). In last decade, some studies have been done for application of polysilicon Nanoparticles in water-wet sandstone (Onyekonwu, 2010; Ju, 2009; Ju, 2002; Ju, 2006; Wang, 2010). In previous investigations, wettability alteration discussed as the main mechanism for increasing recovery efficiency. However, from the view of the literature in this field, there exist lack of fundamental understanding about the mechanism of oil recovery by utilizing neutrally-wet polysilicon (NWP) and hydrophobic Lipophilic polysilicon (HLP) Nanoparticles in enhancing oil recovery(Onyekonwu, 2010). This paper presents a comparison between recovery efficiency of these Nanoparticles in enhancing oil recovery from one of the Iranian oil reservoirs and discuss about main mechanisms contributed in oil recovery.