An Experimental Study of Smart Waterflooding on Fractured Carbonate Reservoirs

Wetting state in many fractured carbonate reservoirs exists between mixed-wet to oil-wet. Interaction of negatively charged carboxylic molecules in the crude oil with the rock surface, and high capillary pressure encountered during oil migration into the reservoir rock frequently render the rock oil-wet. Similarly, the existence of fractures solitarily governs the fluid flow dynamics in the porous media. Therefore, oil recovery from oil-wet fractured reservoirs is extremely tasking due to complex mechanisms involved in interactions between the double porosity system and the reservoir fluids. Waterflooding seems to be an economical technique to recover oil from fractured (water-wet) reservoirs where the rate of oil recovery is controlled by the water imbibition into the matrix from the fracture network. While for oil-wet reservoirs, waterflooding appears feeble and smart waterflooding looks very promising through varying of ions in the injection water. Hence changes the properties of the rock and improves waterflood performance. Middle East carbonate cores, dead crude oil, and smart water of different salinity were used in both static imbibition cells and centrifuge experiments. In order to gain better understanding of the relative contribution of oil recovery between fracture and matrix, different core configurations were used. The tests were carried out initially with formation brine and followed by different slugs of smart water. Presented in this work are the results obtained from the formation brine-oil imbibition tests and smart water-oil imbibition tests in fractured and unfractured cores. Results showed that waterflood recovery from fractured carbonate cores was about 50% of the OOIC while incremental displacement for smart water imbibition was observed nearly as high as 13%.

Download Full-text

An Experimental Study of Wetting Behavior and Surfactant EOR in Carbonates With Model Compounds

SPE Journal ◽

10.2118/99612-pa ◽

2008 ◽

Vol 13 (01) ◽

pp. 26-34 ◽

Cited By ~ 93

Author(s):

Yongfu Wu ◽

Patrick J. Shuler ◽

Mario Blanco ◽

Yongchun Tang ◽

William A. Goddard

Keyword(s):

Oil Recovery ◽

Anionic Surfactants ◽

Fractured Reservoirs ◽

Naphthenic Acids ◽

Carbonate Reservoirs ◽

Reservoir Rock ◽

Intermediate Water ◽

Wetting Behavior ◽

Fractured Carbonate ◽

The Matrix

Summary This study focuses on the mechanisms responsible for enhanced oil recovery (EOR) from fractured carbonate reservoirs by surfactant solutions, and methods to screen for effective chemical formulations quickly. One key to this EOR process is the surfactant solution reversing the wettability of the carbonate surfaces from less water-wet to more water-wet conditions. This effect allows the aqueous phase to imbibe into the matrix spontaneously and expel oil bypassed by a waterflood. This study used different naphthenic acids (NA) dissolved in decane as a model oil to render calcite surfaces less water-wet. Because pure compounds are used, trends in wetting behavior can be related to NA molecular structure as measured by solid adsorption; contact angle; and a novel, simple flotation test with calcite powder. Experiments with different surfactants and NA-treated calcite powder provide information about mechanisms responsible for sought-after reversal to a more water-wet state. Results indicate this flotation test is a useful rapid screening tool to identify better EOR surfactants for carbonates. The study considers the application of surfactants for EOR from carbonate reservoirs. This technology provides a new opportunity for EOR, especially for fractured carbonate, where waterflood response typically is poor and the matrix is a high oil-saturation target. Introduction Typically only approximately a third of the original oil in place (OOIP) is recovered by primary and secondary recovery processes, leaving two-thirds trapped in reservoirs as residual oil. Approximately half of world's discovered oil reserves are in carbonate reservoirs and many of these reservoirs are naturally fractured (Roehl and Choquette 1985). According to a recent review of 100 fractured reservoirs (Allan and Sun 2003), carbonate fractured reservoirs with high matrix porosity and low matrix permeability especially could use EOR processes. The oil recovery from these reservoirs is typically very low by conventional waterflooding, due in part to fractured carbonate reservoirs (about 80%) being originally less water-wet. Injected water will not penetrate easily into a less water-wetting porous matrix and so cannot displace that oil in place. Wettability of carbonate reservoirs has been widely recognized an important parameter in oil recovery by flooding technology (Tong et al. 2002; Morrow and Mason 2001; Zhou et al. 2000; Hirasaki and Zhang 2004). Because altering the wettability of a rock surface to preferentially more water-wet conditions is critical to oil recovery, alteration of reservoir wettability by surfactants has been intensively studied, and many research papers have been published (Spinler and Baldwin 2000). Vijapurapu and Rao (2004) studied the capability of certain ethoxy alcohol surfactants to alter wettability of the Yates reservoir rock to water-wet conditions. Seethepali et al. (2004) reported that several anionic surfactants in the presence of Na2CO3 can change a calcite surface wetted by a West Texas crude oil to intermediate/water-wet conditions as well as, or even better than, an efficient cationic surfactant. Zhang et al. (2004) investigated also the effect of electrolyte concentration, surfactant concentration, and water/oil ratio on wettability alteration. They reported that wettability of calcite surface can be altered to approximately intermediate water-wet to preferentially water-wet conditions with alkaline/anionic surfactant systems. Adsorption of anionic surfactants on a dolomite surface can be significantly reduced in the presence of sodium carbonate.

Download Full-text

Mechanisms of Enhanced Natural Imbibition With Novel Chemicals

SPE Reservoir Evaluation & Engineering ◽

10.2118/113453-pa ◽

2009 ◽

Vol 12 (06) ◽

pp. 912-920 ◽

Cited By ~ 28

Author(s):

Jieyuan Zhang ◽

Quoc P. Nguyen ◽

Adam Flaaten ◽

Gary A. Pope

Keyword(s):

Sodium Carbonate ◽

Oil Recovery ◽

Divalent Cations ◽

Low Cost ◽

Large Body ◽

Carbonate Reservoirs ◽

Alternative Methods ◽

Type I ◽

Water Imbibition ◽

Fractured Carbonate

Summary A large body of literature has reflected an extensive experimental study of natural imbibition driven by local capillary pressures at high interfacial tension (IFT). However, water imbibition induced by emulsification at low IFT is not well understood. Recently, anionic surfactants have been shown to induce imbibition in mixed- and oil-wet carbonates. Sodium carbonate has been used to reduce the surfactant adsorption. However, calcium and other divalent cations can cause precipitation of the alkali unless soft water is used. This is a significant limitation of sodium carbonate. The present research both advances our understanding of the use of chemicals to enhance oil recovery (EOR) from fractured carbonate reservoirs and indicates how the process can be optimized using novel chemicals. This research applies to the improvement of oil recovery from mixed- and oil-wet fractured carbonate reservoirs. We show how to select and evaluate new chemicals as natural imbibition enhancers in carbonate rocks. A novel experimental method has also been developed to quantify the significance of capillary and emulsification driven imbibition because of the presence of the chemical imbibition enhancers. An in situ imbibition profile was visualized using a computed tomography (CT) X-ray scanning technique. The results show that formation of microemulsion strongly promotes water imbibition. The rate was highest for Winsor Type II microemulsion and lowest for Winsor Type I microemulsion. The alkalis exhibited a striking imbibition enhancement driven mainly by alteration of capillary pressure. The performance of the imbibition enhancers was found to be consistent for different core-plug sizes and boundary conditions. A novel alkali has been tested that shows a high tolerance for hardness and, thus, may be a good alternative to sodium carbonate under some conditions. The application of low-cost chemicals to EOR from fractured carbonates is an extremely significant development owing to the vast volumes of oil in such reservoirs and the lack of practical alternative methods of recovering such oil.

Download Full-text

Characterization of Matrix Wettability and Mass Transfer From Matrix to Fractures in Carbonate Reservoirs

Volume 6: Materials Technology; Polar and Arctic Sciences and Technology; Petroleum Technology Symposium ◽

10.1115/omae2012-84172 ◽

2012 ◽

Author(s):

Anuj Gupta

Keyword(s):

Oil Recovery ◽

History Matching ◽

Oil And Gas ◽

Fractured Reservoirs ◽

Naturally Fractured Reservoirs ◽

Carbonate Reservoirs ◽

Shape Factors ◽

Naturally Fractured ◽

Fractured Carbonate ◽

The Matrix

This paper presents results of an experimental investigation, supported by numerical analysis, to characterize oil recovery from fractured carbonate reservoirs. Imbibition recovery of oil is measured as a function of time for samples with varying wettability and shape factors. One of the objectives of this study is to verify the validity of exponential transfer function for matrix-fracture systems with varying wettability and flow-boundary conditions. Another objective is to establish the possibility of quantitatively determining the wettability of a sample based on history-matching of cumulative imbibition recovery and recovery rate data. The productivity of most carbonate oil and gas reservoirs is closely tied to the natural or stimulated fracture system present in the reservoir. Further, the recovery from naturally fractured reservoirs, in presence of aquifer drive or waterflooding is closely tied to the wettability of the matrix. The approach presented in this paper offers means to evaluate how recovery factor in a fractured system can be affected by wettability. A detailed understanding of rock-fluid interactions and wettability alterations at the fracturing face should help design improved strategies for exploiting naturally fractured carbonate reservoirs.

Download Full-text

Wettability alteration and oil recovery by spontaneous imbibition of smart water and surfactants into carbonates

Petroleum Science ◽

10.1007/s12182-019-00412-1 ◽

2020 ◽

Vol 17 (3) ◽

pp. 712-721 ◽

Cited By ~ 8

Author(s):

Saeb Ahmadi ◽

Mostafa Hosseini ◽

Ebrahim Tangestani ◽

Seyyed Ebrahim Mousavi ◽

Mohammad Niazi

Keyword(s):

Contact Angle ◽

Enhanced Oil Recovery ◽

Oil Recovery ◽

Carbonate Rock ◽

Spontaneous Imbibition ◽

Wettability Alteration ◽

Rock Surface ◽

Smart Water ◽

Fractured Carbonate ◽

Enhance Oil Recovery

AbstractNaturally fractured carbonate reservoirs have very low oil recovery efficiency owing to their wettability and tightness of matrix. However, smart water can enhance oil recovery by changing the wettability of the carbonate rock surface from oil-wet to water-wet, and the addition of surfactants can also change surface wettability. In the present study, the effects of a solution of modified seawater with some surfactants, namely C12TAB, SDS, and TritonX-100 (TX-100), on the wettability of carbonate rock were investigated through contact angle measurements. Oil recovery was studied using spontaneous imbibition tests at 25, 70, and 90 °C, followed by thermal gravity analysis to measure the amount of adsorbed material on the carbonate surface. The results indicated that Ca2+, Mg2+, and SO42− ions may alter the carbonate rock wettability from oil-wet to water-wet, with further water wettability obtained at higher concentrations of the ions in modified seawater. Removal of NaCl from the imbibing fluid resulted in a reduced contact angle and significantly enhanced oil recovery. Low oil recoveries were obtained with modified seawater at 25 and 70 °C, but once the temperature was increased to 90 °C, the oil recovery in the spontaneous imbibition experiment increased dramatically. Application of smart water with C12TAB surfactant at 0.1 wt% changed the contact angle from 161° to 52° and enhanced oil recovery to 72%, while the presence of the anionic surfactant SDS at 0.1 wt% in the smart water increased oil recovery to 64.5%. The TGA analysis results indicated that the adsorbed materials on the carbonate surface were minimal for the solution containing seawater with C12TAB at 0.1 wt% (SW + CTAB (0.1 wt%)). Based on the experimental results, a mechanism was proposed for wettability alteration of carbonate rocks using smart water with SDS and C12TAB surfactants.

Download Full-text

Investigation of Smart Water Imbibition Assisted with Microwave Radiation as a Novel Hybrid Method of Enhanced Oil Recovery

Journal of Molecular Liquids ◽

10.1016/j.molliq.2021.116101 ◽

2021 ◽

pp. 116101

Author(s):

Saeed Karami ◽

Amir Hossein Saeedi Dehaghani ◽

Manouchehr Haghighi

Keyword(s):

Microwave Radiation ◽

Enhanced Oil Recovery ◽

Oil Recovery ◽

Hybrid Method ◽

Water Imbibition ◽

Smart Water

Download Full-text

Improved Oil Recovery in Fractured Carbonate Reservoirs: Don't Give Induced Fractures A Chance!

10.2118/98386-ms ◽

2006 ◽

Cited By ~ 2

Author(s):

Dick Jacob Ligthelm ◽

Paul Jacob van den Hoek ◽

Pascal Hos ◽

Marinus J. Faber ◽

Roeland Roeterdink

Keyword(s):

Oil Recovery ◽

Carbonate Reservoirs ◽

Improved Oil Recovery ◽

Fractured Carbonate ◽

Induced Fractures

Download Full-text

Smart water flooding performance in carbonate reservoirs: an experimental approach for tertiary oil recovery

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-019-0650-9 ◽

2019 ◽

Vol 9 (4) ◽

pp. 2643-2657 ◽

Cited By ~ 10

Author(s):

Arman Darvish Sarvestani ◽

Shahab Ayatollahi ◽

Mehdi Bahari Moghaddam

Keyword(s):

Oil Recovery ◽

Experimental Approach ◽

Carbonate Reservoirs ◽

Water Flooding ◽

Smart Water ◽

Tertiary Oil Recovery

Download Full-text

Laboratory study of nitrogen/foam enhanced oil recovery from vuggy-fractured carbonate reservoirs

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/585/1/012037 ◽

2020 ◽

Vol 585 ◽

pp. 012037

Author(s):

Wang Yang ◽

Fan Hongwei ◽

Gong Quanfeng ◽

Xin Dong

Keyword(s):

Enhanced Oil Recovery ◽

Laboratory Study ◽

Oil Recovery ◽

Carbonate Reservoirs ◽

Nitrogen Foam ◽

Fractured Carbonate

Download Full-text

A Surface Complexation Model of Alkaline-SmartWater Electrokinetic Interactions in Carbonates

E3S Web of Conferences ◽

10.1051/e3sconf/202014602003 ◽

2020 ◽

Vol 146 ◽

pp. 02003

Author(s):

Moataz Abu-Al-Saud ◽

Amani Al-Ghamdi ◽

Subhash Ayirala ◽

Mohammed Al-Otaibi

Keyword(s):

Experimental Data ◽

Zeta Potential ◽

Crude Oil ◽

Oil Recovery ◽

Surface Complexation ◽

Surface Complexation Model ◽

Zeta Potentials ◽

Smart Water ◽

Injection Water ◽

Carbonate Formations

Understanding the effect of injection water chemistry is becoming crucial, as it has been recently shown to have a major impact on oil recovery processes in carbonate formations. Various studies have concluded that surface charge alteration is the primary mechanism behind the observed change of wettability towards water-wet due to SmartWater injection in carbonates. Therefore, understanding the surface charges at brine/calcite and brine/crude oil interfaces becomes essential to optimize the injection water compositions for enhanced oil recovery (EOR) in carbonate formations. In this work, the physicochemical interactions of different brine recipes with and without alkali in carbonates are evaluated using Surface Complexation Model (SCM). First, the zeta-potential of brine/calcite and brine/crude oil interfaces are determined for Smart Water, NaCl, and Na2SO4 brines at fixed salinity. The high salinity seawater is also included to provide the baseline for comparison. Then, two types of Alkali (NaOH and Na2CO3) are added at 0.1 wt% concentration to the different brine recipes to verify their effects on the computed zeta-potential values in the SCM framework. The SCM results are compared with experimental data of zeta-potentials obtained with calcite in brine and crude oil in brine suspensions using the same brines and the two alkali concentrations. The SCM results follow the same trends observed in experimental data to reasonably match the zeta-potential values at the calcite/brine interface. Generally, the addition of alkaline drives the zeta-potentials towards more negative values. This trend towards negative zeta-potential is confirmed for the Smart Water recipe with the impact being more pronounced for Na2CO3 due to the presence of divalent anion carbonate (CO3)-2. Some discrepancy in the zeta-potential magnitude between the SCM results and experiments is observed at the brine/crude oil interface with the addition of alkali. This discrepancy can be attributed to neglecting the reaction of carboxylic acid groups in the crude oil with strong alkali as NaOH and Na2CO3. The novelty of this work is that it clearly validates the SCM results with experimental zeta-potential data to determine the physicochemical interaction of alkaline chemicals with SmartWater in carbonates. These modeling results provide new insights on defining optimal SmartWater compositions to synergize with alkaline chemicals to further improve oil recovery in carbonate reservoirs.

Download Full-text