Surfactants in Upstream E&P

Surfactants are defined as molecules able to lower the surface (or interfacial) tension at the gas/liquid, liquid/liquid, and liquid/solid interfaces. Due to their properties, they are typically employed as detergents, emulsifiers, dispersants, wetting and foaming agents. In chemical enhanced oil recovery (cEOR), surfactants are used as flooding agents, alone or in combination with polymers, alkali, and more recently nanoparticles, to increase the microscopic displacement efficiency. From a chemical point of view, surfactants are amphiphiles, meaning that they bear in their structure both hydrophilic and hydrophobic moieties. Some naturally occurring surfactants exists, but the majority are synthetic. The availability of synthetic surfactants, allows a big variety of structures and properties. In this chapter, the main classes of surfactants will be reviewed, with focus on those used or proposed for use for chemical enhanced oil recovery. After a general introduction about surfactants and their main structural and physico-chemical properties, specific aspects of design and synthesis will be discussed. Particular emphasis will be given to the most recent developments, which includes zwitterionic, gemini and polymeric surfactants. Own work of the author of this chapter in the field of polymeric surfactants will be highlighted.

This chapter is divided into eight different sections. The first three sections describes the introduction of drilling fluid in general and drilling fluid types along with the major drilling fluid additives, major problems of drilling fluids (related to the shale swelling and hydration), Solution of shale swelling and hydration (emphasis on the use of surfactants). It also discusses about the classification and synthesis of surfactants that are used in the formulation of drilling fluids and potential application for shale inhibitions. The next three of this chapter discusses about the impact of surfactants on rheology and filtration properties, and the evaluation of shale inhibition characteristics with surfactant which has explained all the techniques involved in characterizing drilling fluids for shale inhibition. The last two sections of this chapter discusses about the field applications, recommendations and challenges of surfactants for shale inhibition.

In the formulation of drilling fluids, different additives are used to optimize their rheological behavior and control the fluid loss throughout the drilling process. Surfactants, as one of these additives, play a vital role in sealing off the lost circulation zones and in controlling the rheological properties of the dispersions to meet the specification of the desired applications. This chapter is divided into three sections. The first section reviews the definition, functions, and properties of drilling fluids, bentonites and surfactants. The second section provides an overview on the main and recent research on utilization of surfactants in drilling fluid formulations. The last section describes an experimental work on the effect of cationic surfactant CTAB and anionic surfactant SDS on the performance of water based drilling fluid. Adding of CTAB surfactant to water-based drilling fluid reduced significantly its viscosity and shifted its rheological behavior from shear thinning fluid with a yield stress towards Newtonian behavior. On the other hand, the SDS surfactant was effective in modifying the rheological properties of water-based drilling fluid in the concentration range that corresponds to critical micelle concentration (CMC) and critical coagulation concentrations (CCC) of SDS.

In general, it is believed that the ultra-low IFT provided by surfactant is a requirement for the higher microscopic recovery efficiency during enhanced oil recovery (EOR). In tight oil shale and shale reservoirs, capillary imbibition become a dominant recovery mechanism where ultra-low IFT becomes less significant or even a retarding force in certain scenarios. Recent researches have emphasized that the microscopic efficiency of CO₂ flooding could be improved by adding low IFT surfactants. Surfactants are also used for conformance/mobility control applications in the form of foam. During foam flooding application in naturally fractured reservoirs, the ultra low-IFT conditions is advantageous for oil recovery in dolomite but not in limestone rocks. Although low-IFT conditions positively influences the microscopic recovery during alkali steam-foam flooding, ultra-low IFT is not required. This chapter compiles these cases and sheds insight using fundamental reservoir engineering concepts to understand why the ultra-low IFT conditions, conventionally considered to be a prerequisite for the higher residual oil recovery, are not always beneficial or required or enough during many of the EOR applications.

It is well recognized that ultra-low interfacial tension (IFT) from formation of middle-phase microemulsion is a must in surfactant-based EOR process. However, high concentration of surfactant or surfactant mixtures is generally needed, and it remains unknown how surfactant micelles evolve when they contact oil in porous media. More importantly, few case stories of such microemulsion flooding were reported yet so far. In China, low concentration (<0.3wt%) surfactant slug is always employed with polymer slugs to form binary systems, and more than 15% oil recovery factor has been obtained from field trials. In this chapter, we proposed alternative mechanisms by reviewing our preliminary laboratory results of micellar solubilization of oils and in-situ emulsification with either model surfactant or practically used commodity surfactants. The results show that higher oil recovery factors can be obtained without reaching ultra-low IFT. These findings may provide new guidelines to design surfactant-containing flooding systems for chemically enhanced oil recovery.

This chapter discusses about the application and potential role of biosurfactants in oil recovery technology. The mechanism of mobilizing of trapped crude oil within the pores of reservoir rocks has been discussed on the basis of reduction of interfacial tension (IFT), wettability alteration, emulsion formation, and biodegradation of oil. In situ production and ex situ injection of biosurfactants for different suitable microbial strains have been reviewed and laboratory based evaluation of microbial enhanced oil recovery (MEOR) have been discussed. Internationally major field trials of MEOR by worlds leading oil producing nations have been reported. Thus, this chapter tries to concentrate on nearly all the concern issues about the past, latest trends and potential aspects of biosurfactants applications in oil recovery.

After the primary and secondary methods of hydrocarbon production, the reservoir depletes and often relies on enhanced oil recovery techniques (EOR, a tertiary method) to reduce the residual oil saturation (S_or) to a minimum value. Amongst many methods, the chemical EOR (cEOR) technique of oil recovery is widely implemented. The cEOR technique aims to optimize mobility ratio and reduce interfacial tension (IFT) and the viscosity of in situ oil. A subclass of cEOR is surfactant flooding which uses the principle of IFT reduction to facilitate additional oil gain. This process incorporates the use of surfactants which promotes favorable wettability and forms in situ oil–water (o/w) emulsions driving the oil towards the producing well. This chapter provides insight into different classes and types of surfactants used in cEOR methods. The discussions on different surfactants are carried out broadly in terms of its effect on IFT, temperature stability, adsorption on rock matrix and effectiveness in saline environments.

The need for effective enhanced oil recovery (EOR) methods in terms of economics and technical feasibility are growing rapidly along with the steeply growing demand for crude oil in the energy sector. Such demands driving researchers to innovate novel EOR solutions and also to explore ways to enhance the effectiveness of conventional EOR methods. This chapter summarises advancement in one such hybrid EOR method developed by combining novel low salinity water flooding with conventional surfactant flooding. The synergistic benefits of low salinity water and different low salinity surfactant formulations in terms of improving reservoir properties and oil recovery efficiency are summarized. This chapter also aims to provide a very detailed discussion on the complex pore level mechanism of oil recovery through the hybrid low salinity surfactant flooding process.

Surfactants and gel treatments are two major types of chemicals that have gained a great deal of attention in the oil industry due to their oil recovery enhancement and water shutoff improvement. The surfactants are mainly used to improve the microscopic displacement efficiency or change the rock wettability from oil wet to oil wet for oil recovery improvement, while gel treatments are often used to significantly reduce the fluid flow through channels or fracture and thus improve water flooding efficiency. The combination of these two methods have a great potential to significantly improve oil recovery in both micro- and macro-scope. This chapter first reviews the fundamentals of surfactants, conventional nanoparticles, polymeric nanoparticles and preformed gel particles that are often used in EOR applications. Then, it describes how the combination of surfactants with these particles can be used to significantly enhance oil recovery in terms of their mechanisms and laboratory experimental results.

This chapter describes the application of surfactant-based foams for recovery of oil with a focus on subsurface aspects. While the concept of foaming may be qualitatively well understood, the physical behaviour of a foam system comprising gas, brine, and surfactant depends on the type of each of these three constituents and their interaction, in addition to the properties of the porous medium in which the foam is designed to be generated and perhaps propagate. Key physical properties, which must be investigated during a laboratory experimental program, are discussed. A critical review is provided of a number of key applications where foam is utilised for recovery of oil, starting with drilling, completion, and stimulation before moving on to chemical conformance and enhanced oil recovery.

In foam displacement for better oil recovery foamability along with foam, stability is considered among the significant concerns. The generation of foam is not much of a challenge as compared to foam stability. It is affected by many factors. Also, the selection of right surfactants is of more importance.

Oil and gas recovery from subsurface reservoir formations requires the application of appropriate stimulation and production techniques, aimed at restoring sufficient pressure difference within drilled formations. Proper implementation of surfactants aids in enhanced fluid connectivity of the reservoir at initial stages of well stimulation, as well as maintain long-term hydrocarbon production. Nowadays, it is being considered as an effective alternative to conventional fracturing fluids such as polymers, gels, etc. due to low cost of application, alteration of inter-molecular interactions, and prevention of insoluble residues’ formation. It is evident that the physicochemical attributes of surfactant-based fracturing fluids can be suitably modified through the use of combination of additives such as friction reducers, clay stabilizers, acids, iron-control agents, cross-linking agents, non-emulsifiers, buffers, inhibition agents, gels, and associated gel breakers. The primary objective of this method lies in minimizing the extent of oil-water block near the wellbore matric and develop pore-connectivity in hydrocarbon pay-zones to attain good recovery characteristics. Surfactant fracturing fluids, if injected properly, are capable of reducing flowback, improving fluid stability and effective clean-up. Therefore, it is a possible route for petroleum engineers and fracture design professionals to produce oil and gas from low permeability reservoir zones via hydraulic fracturing technique, whilst attaining maximum recovery efficacy, production rate and economical operation. This chapter provides a detailed description of design and methodology of surfactants as fracturing fluids in the petroleum industry.

Development and application of technology to achieve and maintain economic production rates from oil and gas wells has always been a central challenge in the oil and gas industry. The challenge can, in simple terms, be defined as how one can maximize the surface area that dictates the communication between the subsurface and the well, while at the same time, improve the flow of hydrocarbons from the stimulated drainage area/volume into the well. In this Chapter, we provide a review of the use of surfactants in well stimulation. We start with a brief overview of the various mechanisms by which surfactants can be used to achieve specific goals. We then provide a summary of laboratory-scale efforts and observations related to the application of surfactants. Reports and findings from field-scale application/tests are then summarized, and we complete the Chapter with a review of novel developments/applications that are currently subject to research.

Surface active agents (surfactants) are abundant in nature, manufacturing, and daily life. They find applications in various petroleum production operations. This chapter discusses many applications of surfactants as corrosion inhibitors in the petroleum industry like as oil and gas production, refinery processes, water flooding, acid retarders (acid corrosion inhibitor) in both acidization of oil and gas wells and chemical cleaning processes for heat exchangers, separator vessels, drain of oil and gas production stations, water flooding stations in addition to cooling tower treatment. The higher inhibition efficiency of surfactants as corrosion inhibitors is due to adequate solubility and rate of migration of the inhibitor from the bulk solution to the metal surface. In addition, strong binding of the surfactant head groups to the metal surface and self-assembly of hydrocarbon tails to form a hydrophobic barrier.

This chapter provides an introductory understanding of the role of surfactants in the formation of gas hydrates. The main theories that have been developed over the past decades are discussed with support from computational aspects that have become increasingly useful in this regard. Particularly for surfactants, the structure-property relations are key in the full understanding of their behavior in the context of hydrate formation kinetics and equilibria, which are presented with evidence from various studies. Furthermore, surfactants can benefit from co-promoters that may be utilized in hydrate formation, so we present some details to highlight the importance of their interactions. More recently, bio-based surfactants have gained interest out of environmental concerns, and we showcase some of the most interesting cases of their implementation. Although there have been many examples of how gas hydrates can be used for cold storage, hydrogen storage, and other industrial applications, the usage of surfactants or other additives has not been well supported with clear fundamental understandings. Thus, there have been endeavors to gain these insights via computational tools that span different scales, like quantum mechanics and molecular dynamic simulations. The use of these tools is explained with examples. Combining all these different aspects, we hope to provide some understanding of the role of surfactants in current and emerging hydrate management technologies.

Emulsions are thermodynamically unstable systems, since they will separate to reduce the interfacial area between the oil phase and the water phase, as a function of time. As a metastable system, surfactant molecules, amphiphilic polymers or solid particles must be present before a stable emulsion system is formed. These components of an emulsion system are called emulsifiers. The relative balance of the hydrophilic and lipophilic properties of these emulsifiers is known to be the most important parameter dictating the emulsion type, whether an oil-in-water (o/w) or water-in-oil (w/o) emulsion. Irrespective of the emulsion type formed, demulsification is a costly exercise in the oil and gas industry. This chapter describes the fundamental role played by surface active agents (surfactants) as integral components of a chemical demulsifier.