A TECHNICAL REVIEW ON NEWLY FORMULATED OIL-BASED DRILLING FLUIDS

ABSTRACT

In recent decades, environmental issues surrounding the use of conventional diesel oil-based drilling fluids are on the increase. This have forced companies to develop drilling fluid which are safe and friendlier to the environment. It is imperative to find the best amongst the drilling fluid developed that can serve as a viable replacement for diesel oil-based fluid.  In this study, a review was carried out by comparing castor, almond, groundnut, soybean, jatropha oil and diesel oil-based fluid. To determine their suitability as drilling fluids, the physicochemical properties (Oil density, Oil viscosity, Flash point), rheological properties (Mud Density, Mud pH, Mud Viscosity, Gel strength, and filtration) and toxicity test obtained from already analyzed primary data reported in scientific journals. The results from the comparison of the physicochemical properties of the oils indicated that all the oil samples have properties better than diesel oil, and thus qualify to be used as base oils in drilling fluids. The results from the comparison of different rheological properties of the newly formulated oil-based fluids showed great viability for the fluids to be used as replacement for diesel-based oil fluid. The rheological properties of soybean and jatropha oil-based fluid obtained from authors are yield point Ib/100ft² and 10 Ib/100ft² respectively, plastic viscosity 14cp and 14cp respectively, gel strength @10secs is 5 Ib/100ft² and 6 Ib/100ft² and the gel strength at @ 10mins is 6 Ib/100ft² and 7 Ib/100ft² respectively. Toxicity results obtained from previous authors proved these newly formulated oil-based fluids are less toxic and biodegradable when compared to diesel oil-based drilling fluids. A cost analysis of the newly formulated oil-based drilling fluids was also carried out comparing the prices of soybean, groundnut, almond, and diesel oil in the last four years (2018-2021). The cost per gallon of soybean, almond, and groundnut oil in the last three years (2018-2021) were higher than diesel oil. however, the advantages of these drilling fluids such as cuttings disposal cost reduced due to these fluids’ biodegradability nature makes it desirable regardless of its high cost.

CHAPTER 1

 

1.0 Introduction

 

The global demand for energy is on the increase because of the rapidly increasing population and economies. With this increasing demand for energy comes an increase in the exploration and development of energy sources such as petroleum reserves. Drilling is a very important step when it comes to oilfield development, this is because the objective of the operation is to safely reach the targeted reserves in the shortest time possible and at the most affordable cost with additional problems arising due to sampling and evaluation constraints of the process (Khodja et al, 2010). The success of the drilling operation depends on the information gotten from the geologically drilled formation and good reservoir conditions and especially the performance of the drilling fluid.

The drilling fluid is a major component of the oil well drilling operation which is often referred to as “the blood of the drilling process”, the cost is estimated to cover about 5%-15% of the total drilling cost of a well (Boyl et al.,1994).It usually is a mixture of liquid, solid, and gas which is circulated in the wellbore to help achieve a low cost and efficient drilling process (S. Gandhi & B. Sarkar, 2016). The fluid plays a significant role and performs numerous functions throughout the entire drilling process (Agwu et al 2017). These functions include transporting the drill cuttings from the bottom of the hole to the surface, cooling and lubricating the drilling bit as well as the drill string to minimize its wear, sealing off permeable formations by forming an impermeable relatively thin mud cake at the borehole wall of the permeable formations, creating an overbalanced drilling condition to control the formation pressure, hold drill cuttings in suspension when circulation is interrupted, creating a buoyancy force to partly support the weight of the drill string and casing string, reduction of formation damage of various horizons penetrated, transmission of hydraulic horsepower to the bit and allowing maximum penetration rates, and carrying downhole information from the drilled well in form of signals to the surface for interpretation. Therefore, the success of any drilling operation is hinged on the performance of the drilling fluid used for the drilling operation (Wedman Ahmed & Kalkan, 2019). These fluids are usually classified based on their component mixture and base fluid content as:

• Water based drilling fluid (WBF)

These fluids may be fresh water, seawater, brine, saturated brine, or a formate brine. It falls into two categories dispersed and non-dispersed mud

• Oil-based drilling fluid (OBF)

These fluids are formulated with diesel, mineral oil, or low-toxicity linear olefins and paraffins. They have more advantageous properties compared with water-based drilling fluid i.e. shale inhibition, thermal stability, reduction of torque and drag problems etc.

• Pneumatic based drilling fluid

It comprises of air, mist, and foam gas, they are generally used for poorly consolidated and fractured formations. It has been confirmed by controlled drilling rate test conducted in various rock that air or gas is a faster drilling than water or oil.

Since the 1930s, it has been discovered that oil-based fluid (OBF) achieved better productivity than water-based fluid (WBF) which have enabled the upstream of the petroleum industry thrive on OBF.

The effectiveness or the performance of the drilling fluid is dependent also on their rheological properties that is, the material properties that govern the specific way in which the deformation or flow behaviours occur (L. Figura & A. Teixeira, 2007). Examples of these rheological properties include plastic viscosity, yield point, gel strength and apparent viscosity (S. Elkatatny et al, 2016).

As explorationists make discoveries in unconventional terrains such as deep-water offshore fields, ultra-high temperature, high pressure fields, arctic regions, and other hostile environments, the cost of drilling for oil and gas reserves becomes more expensive.

For any successful drilling operation, high performance rate of the circulating drilling fluid is required (Fadairo et al, 2012). During drilling, the selection of a drilling fluid type generally begins with choosing a drilling fluid family in accordance with the nature of the rock formation while taking into consideration its cost implications and environmental impacts (Nwaiche, 2015).

The following factors are prominence in the selection of a drilling fluid:

• Well design
• Formation pressure
• Rock mechanics
• Chemistry of the formation
• Limiting negative impacts on the producing formation
• Environmental issues and regulations
• Logistics
• Cost

Over the years, the drilling industry has utilized two sorts of drilling fluids, namely, water-based fluid and oil-based drilling fluid. Water-based fluid is cost-effective and easily formulated hence it is commonly utilized as a drilling fluid while oil-based fluid is more costly compared to waterbased fluid. The oil-based fluid in spite of being less cost effective, they are utilized because of its corrosion control property, its exceptional lubricating property and its great rheological properties at temperature as high as 500 F showing better stability behaviour. Oil-based drilling fluids can also drill through formations containing water swellable clays. Diesel oil is used as the base fluid to formulate an oil-based drilling fluid due to its low flammability, low solvency for rubber, and high viscosity (Agwu et al 2015).

The use of OBF has special considerations. These include cost and environmental considerations (disposal of cutting in an appropriate place to isolate possible environmental contaminations). Based on this, the type of oil used must be taken into consideration when formulating OBF.

Stakeholders in the petroleum industry have been tasked with the challenge of finding a solution to this problem by formulating optimum drilling fluids and also reduce the handling cost and negative environmental impacts on the conventional diesel-based drilling fluid (Ose et al, 2019). The research area of determining a substitute for the conventional diesel oil-based fluid to meet the environmental specifications is relatively new.

Researches have been carried out to discover and formulate oils that can mitigate the environmental problems. Hence, synthetic oil-based fluid was discovered which possess low toxicity and high biodegradability. It is very important to increase the use of environmentally friendly and biodegradable sources of oil to formulate our OBF, thereby making it less expensive and environmentally safe and equally maintaining the basic functions of the drilling fluid such as maintaining of hydrostatic pressure, removal of cutting, cooling and lubricating the drill string and also to keep newly drilled borehole open until cementing is carried out (Yassin et al,1990).

 

1.1. Motivation

 

The application of oil-based drilling fluids has proven to be efficient in oil field development. Though efficient, many challenges have risen due to the use of the conventional oil-based drilling fluid, which is mostly environmental. Steps have been taken in order to eliminate these environmental challenges which are caused by the use of the conventional diesel-oil based drilling fluid by formulating a more environmentally friendly oil-based drilling fluid using mineral oils such as oil such as soya bean oil, castor oil, groundnut oil etc.

The results of the research works carried out brought about different outcomes such as variation in terms of their properties, cost and efficiency etc. Hence, this variation has brought about a need for the research and compilation/ comparison of the different oil-based drilling fluid so far developed to help access the most economical and reliable, yet acceptable and beneficial to the oil and gas industry.

1.2. Aim

To analyse the results from the formulation of different newly formulated oil-based drilling fluids

1.3. Objectives

 

To review works on newly formulated oil-based drilling fluid

To determine the desirable properties of newly formulated oil-based drilling fluid

To determine the qualitative properties of diesel oil-based drilling fluid

To make a comparison of the newly formulated oil-based drilling fluid and the conventional diesel oil-based drilling fluid

To determine the best environmentally friendly oil-based drilling fluid

To make an economic analysis of the newly formulated oil-based drilling fluid

A TECHNICAL REVIEW ON NEWLY FORMULATED OIL-BASED DRILLING FLUIDS

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