Chemical Shale Instability & Inhibition - Research Paper Example

Chemical Shale Instability & Inhibition Project the topic listed above has to do with the shale fluid interactions when drilling an oil/gas well. Instructions for Paper Paper should be written as if it were to be published as a scholarly work so no title page no table of contents. Abstract In this paper the main aim is at exploring the complexity and stabiklity of clay rich shale (REFF). This is because it has been revealed that the complexity and chemical interactions of shales with their selected drilling fluids profoundly affect the stability of the shales (REFF). The re is vast need to research and establish the truth. Is there any relationship between phyisiological transport process for example capillarity, osmosis and diffusion and physical change for example loss of hydraulic overbalance due to mud pressure penetration (REFF). Understanding the overall behavior of shale is the core intention of this paper. Furthermore, the discussion is also aiming at understanding various types of shale drilling fluids. This also includes the use of the drilling fluids and their composition. The other key concept explored in te discussion is the mechanism involved in the development of new shale. Introduction Shale can be defined as a sedimentary rock which is fine grained and is composed of mineral rich mud. The mineral composition found in this mud is variable. When discussing about shale instability and inhibition. It is prudent to note that the interaction between water and the clay like material forung within the shale is the root cause (REFF). This interaction contributes to wellbore instability which thereafter result in formation of poor gause and many other anomalies. This paper targets discussing issue related to shale instability and inhibition, challenges faced and how to prevent such inconvenient precisely when drilling shale. Discussion a. The use of drilling fluids in respect to the different types of shales that may be encountered for an elaborate smooth shale drilling, the rotary drilling system must be working properly. To achieve this, there is need to ensure that drilling fluid circulation is taking place continuously. The fluid must have ability to percolate down the drilling pipes and out through the bit nozzle to the surface (REFF). There are many types of drilling fluids that serve different purpose based on the shale being encountered. For example; the drilling fluid can be air, liquid or foam which is colloid of liquid and air (REFF). Notable to mention is tat drilling fluids are in most cases reffered to drilling mud. The wider varieties of drilling mud occur due to variation in chemical and physical properties. All these properties are well and carefully incorporated for specific roles and probably in solving drilling related challenges. The first role of drilling mud is for cooling and lubrication. As the drilling of the shale is taking place, the bit drills into the rocks result in friction due to the rotation of the bits against the rocks surface (REFF). As a result of friction, heat is generated. The role of the drilling mud at this point is to dissipate the heat by circulating the drilling fluids (REFF). Moreover, the drilling mud also lubricates the bits and reduces friction. The other purpose of the drilling mud is cuttings removal. This is a very important function since after the bits engage with the rocks, the cutting formed are supposed to e removed. The drilling fluids serves the purpose of carrying the rocks cuttings to the surface . (Membrane efficiency: the por pressure transmission measurement apparatus for gauging membrane efficiency of various fluids. (REFF) http://www.iadc.org/dcpi/dc-mayjun00/m-baroid.pdf . b. The properties of individual drilling fluids in relation to the wellbore stability while drilling in the vertical, curve, and lateral sections. There are several types of shale drilling fluids which are employed depending on the purpose, wellbore stability and the section of the drilling. To fully elaborate property of each type of drilling fluid used, it is relevant to also know the factor considered most when selecting the type of drilling fluid. Shale drilling fluids are selected based on the cost, technical performance and impact of the fluid on the environment (REFF). This are the three categories analyzed first before making the choice of the drilling fluid to be used. This forms part of a successful shale drilling operation.. Water based shale fluid (WBFs) is the first type of drilling fluid used in drilling shale. Notable to mention is that WBFs is not only considered to be less expensive, but is also the most widely used system as compared to the other fluids (REFF). The WBFs systems has another very important property that suits it better in cases of extreme temperatures. The system is capable of tolerating relatively high down hole temperatures primarily when formulated with invert-emulsion (REFF). Alternatively, water base fluid is commonly deployed in approximately 80% of drilling of shale wells. There is no choice of the type of water to be used. This is an advantage for the drillers since they can use any type of water be it fresh, brine, saturated brine, formate brine or sea water (REFF). The only factor that can result in selection of type of water to be used is the anticipated condition of the well or the specific interval of the well being drilled (REFF). The type of well depending on soil and underground condition dictate the choice of water to be used. When the surface typically is being drilled with low density water, these systems do incorporate natural clays in the curse of the drillingoperation (REFF). Therefore, there must be addition of some commercial bentonite to the fluid to help in the fluid-loss control. Furthermore, this commercial additive will also aid in enhancing hole cleaning effectiveness (REFF). This will continue until when surface casting is set and cemented. At this point, the drilling resume the use of water as previous until maybe unfortunate thing that need changeover happens. Dril-in fluid (DFI) This is another type of shale drilling fluid. The fluid is clean and mostly designed to cause very little or no loss of the natural permeability of pay zone (REFF). DFI is mostly preferred when drilling horizontal wells. It is on horizontal wells where there is likelihood of the drilling fluid being exposed to the pay zone for longer intervals. DFI os considered to be the safest and ideal drilling fluid which is also economical. The fluid is normally compartible with the reserviour native fluid and this aid in preventing precipitation of salt or production of emulsion (REFF). Oil based fluids (OBFs) was first detected and used in the year 1960s. the drilling fluid is basically formulated with diesel , mineral oil and even low-toxicity linear olefins and paraffins (REFF). The two (olefins and paraffins) are normally regarded to be the synthetic. This is so despite some being derived from fractional distillation of crude oil whereas some are chemically synthesized from smaller ,molecules (REFF). The oil based system should practically be incorporated with an emulsion that must be strong enough. The strength should be able to handle wate volume especially when the downhole water flow is encountered (REFF). Shale inhibition is one of the most key benefirt of inrorporating OBFs. This is because, OBFs also uses higher salinity water phase that prevents it from hydrating, swelling and sloughing into the wellbore (REFF). To supplement on this, most oil-based systems are literary formulated with calcium chloride brine which offers the best inhibition propersty for ost shales (REFF) In OBFs, the ratio of incorporation at liquid phase between water and oil normally ranges from 65/35 to 95/5 (REFF). Synthetic based fluids (SBFs) This were specifically developed as a measure of controlling environmental pollution. This was mostly applicable to offshore drillingoperations. The fact that during offshore drilling no discharge is allowed by the set regulation, this is not the case with SBFs. Although it costly but they very economical. They are fast interms of penentration rates and bear less mud-related nonproductive time (NPT) (REFF). SBFs are formulated withlinear alphaolefins (LAO) together with isomerized olefins (IO) which exhibits lower kinetic viscousity required to respond against increasing viscousity of deerper waters (REFF). In addition to this, in the year 2000, a shorter chain length C8 comprising of a low-viscosity ester was developed (REFF). This had higher biodegradability and lower toxicity making it the world most recognizable drilling fluid for environmental performance (REFF). Petriwiki. Drilling Fluids Types. 2013. http://petrowiki.spe.org/Drilling_fluid_types c. The development of new shale inhibitors when encountering shale during drilling peration, the water in the drilling fluid may get into close contact and interact with the clay materials withing the formation and result in shale swelling (REFF). The outcome of such error is broad instability in the wellbore. Furthermore, such error may also result in sloughing which is the dispersion of the shale into the drilling fluid that can literary cause hole washout (REFF). Depending on individual wellbore needs, there are various ned developed types of shale inhibitors. These inhibitors are categorized based on the degree of molecular weight, iconicity and product form to cater on different conditions and fluid systems (REFF). The shale inhibitor products ranges from hydration inhibition to multifunctional polymers that provides additional viscousity and carying capacity (REFF). To begin with, is the Novel cationic-based drilling fluids additive that provides excellent shale inhibition (REFF). This inhibitor forms part on newly tested and inmproved profile on environmental effects. The inhibitor is specifically composed of low-molecular-weight bis-quaternary amines with similar structures to naturary occurring cationic compounds (REFF). The fundamental role of the compound is to ensure there is low toxicity and the properties for shale inhibition are high. Patel, Arvind. 2009. Design and Development of Quaternary Amine Compounds: Shale Inhibition With Improved Environmental Profile. Society of Petroleum Engineers. 1: 978. Extension of the latest amine shale inhibitor chemistries have aided in the design and development of the newcationic amine shale inhibitor (REFF). The is inhibitor serve in providing shale inhibition precisely on water sensitive shale. The inhibition offer is also environmental sensitive since it bears limited toxicity in addition to the excellent shale inhibition. When it comes to biodegradable shale inhibitors, peimary amine with hydrophobic groups is one of the newly developed shale inhibitor which has an excellent performance since it has optimal structures (REFF). In this typr, a balance is developed between the molecular weight of the inhibitor and the hydrophobic lenth that generates peak shale inhibition (REFF). Notable to mention is the fact that shale recovery is propergated by the increase in hydrophobicity of the molecules. Alternatively, when there is increasing branching of the wellbore, the shale recovery becomes very easy. However, the recovery rate is also lowered when by the hardness of the cuttings increases and the molecular weight of the inhibitor decreases the possibility of shale recovery (REFF). Drillingcontractors.org. 2013. Biodegradable Shale Inhibitor Developed for Water Based Muds. http://www.drillingcontractor.org/biodegradable-shale-inhibitor-developed-for-water-based-muds-24172 The alcomer readily disperable (RD) is another very well technically advanced shale inhibitor used in most shale drilling. The product displays the best disperability by creating a minimum viscosity. Despite being a beaded polymer, alcomer RD offers the highest solubility efficiency primarily I shales located in cold conditions. It is easy to mix and bear minimum dust. It has low and well controlled molecular weight. This property ensures that the shale is inhibited from developing excess viscosity when mixing with non-dispersed mud (REFF). The alcomer RD shale inhibitor can also be used in mud concentrates since it allows shipping of upto half the volume of mud, which can then be diluted on site (REFF). Basf.com. 2013. http://www.oilfield-solutions.basf.com/ev/internet/oilfield-solutions/en_GB/applications/drilling/shale-inhibitors Works cited 1. *Shale Inhibition: What Works?, Sandra Gomez and Arvind Patel, M-I SWACO, A Schlumberger Company, 2013, SPE 164108 2. Design and Development of Quaternary Amine Compounds: Shale Inhibition with Improved Environmental Profile, Arvind D. Patel, M-I SWACO, 2009, SPE 121737 3. *Shale-Fluid Interactions and Drilling Fluid Designs, Wenwu He, Sandra L. Gomez, Russel S. Leonard, and David T. Li, M-I SWACO, a Schlumberger Company, 2014, IPTC 17235 4. Silicate-Based Drilling Fluids Deliver Optimum Shale Inhibition and Wellbore Stability, Tomislav Soric, INA Naftaplin; Pavel Marinescu, SPE, M-I Drilling Fluids; and Robert Huelke, SPE, M-I Drilling Fluids, 2004, IADC/SPE 87133 2. 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