It is apparent to us all that drilling activities whether it be for production, repair and injection purposes, causes pollution. For example, during drilling operations, hydrocarbon pollutants such as engine oil, diesel, lubricants and chemicals are being released into nature. After the completion of the drilling operation, if the drilling wastes are left with unprincipled design in the lands adjacent to the well, it will have negative and irreparable effects on the environment.

Furthermore, field constructions such as construction of drilling platform, access roads, communication roads, fluid transmission pipelines and ancillary facilities, if done without environmental studies, can cause the destruction of soil texture, surface and underground water and plant communities of drilling areas.

During the drilling process, the hazardous fluid mixes with oil, water and other chemicals to form a toxic drilling composition. This mixture contains toxic chemicals such as Petroleum, Suspension, Phenol, Arsenic, Chromium, Cadmium, Lead and Mercury, natural radioactive materials and Barium. This composition varies depending on the position and depth of the well and the type of drilling fluid used.

With the increasing focus on the use of environmentally friendly activities, many companies have put green supply chain management on their agenda. Because today, more than ever, concerns about the impact of industrial organizations, on the environment have increased. By adding the concept of “green” to the concept of supply chain management, researchers have addressed the issue of the direct relationship between supply chain and environmental issues.

Having green supply chain has many benefits for companies, both individually and nationally. At the individual level, it brings benefits such as lower costs, greener products and better interaction with suppliers. At the national level, the green supply chain can create markets for green products and also make suppliers more aware of environmental issues. A green supply chain can improve a company’s competitive position by reducing costs.

Green supply chain management

Green supply chain management integrates supply chain management with environmental requirements in all stages of product production, thus integrating the environmental process in supply chain management. This pros from product design to final product delivery to consumers and end-to-end management of each product after its useful life, is called green supply chain management.

The production stages of a product usually include product design, selection and supply of raw materials, production and manufacturing, distribution and transfer processes, delivery to the customer and finally after consumption, recycling and reuse management in order to maximize energy efficiency and associated resources. This type of procedure improves the performance of the entire supply chain.

Supply chain management, which encompasses all activities related to the conversion of goods from the raw material stage to delivery to the final consumer in parallel with the flow of information throughout the supply chain, has a significant impact on the environment. In today’s industry, due to the shortening of the life cycle and the variety of products, decision-making in supply chain management has its sensitivity. Green supply chains and traditional supply chains are different in many aspects. First, traditional chains often focus on economic goals and values. Meanwhile, green chains pay a lot of attention to environmental causes. On the other hand, the green supply chain is ecologically integrated and optimal, and also pays attention to the adverse ecological effects on the natural environment. Ecological requirements are considered as key criteria for products.

Buyer and seller selection criteria are also fundamentally different in the green and traditional supply chain. In traditional chains, price often specifies the standard. But in green chains, environmental goals are part of the criteria for selecting suppliers. Putting these environmental criteria in the evaluation of suppliers means that only a very limited number of suppliers meet the defined criteria. Based on such variables, suppliers can be selected and identified as suitable for green supply chain.

Drilling fluid and its functions

Drilling fluid or drilling mud can be defined as any fluid that circulates inside the well during drilling operations. This fluid returns to the surface after passing through the drill string through the annular space. Drilling fluid can be considered as the most important and main component of drilling operations.  The success of a drilling operation strongly depends on the correct operation of the drilling fluid. When a problem occurs in the drilling operation, the cause of the problem is usually first approached by evaluating the status of the drilling fluid/mud properties.

Drilling fluids have various and vital roles in oil, gas and water wells drilling. Functions that if performed improperly, drilling operations will be no longer be possible. The most important functions of drilling fluids are:

• Suspend drilling materials and release them on the surface

• Extraction of drilling materials from wells

• Subsurface pressure control

• Create a layer on the good wall

• Creating stability in the well

• Cooling, drilling lubrication

Types of drilling fluids

Drilling fluids are generally divided into three types: liquid, gaseous, and mixture. Liquid phase drilling mud includes water base mud and oil base mud. Gas phase drilling mud includes air and natural gas. Understanding the types of drilling fluids in Green drilling fluid supply chain management significantly contributes to environmental goals, reducing material waste and entering additional materials into the environment.

Water-based mud is a fluid in which the main phase is water. To have mud with suitable properties, other substances must be added to water. Many drills use water initially alone. When water is mixed with drilling particles during the drilling operation, this forms what is known as mud.

Oil-based mud is a fluid in which the continuous phase is oil-based fluid. It composes of liquid hydrocarbons and most common fluid is diesel. Water is also used in this mud as an emulsion. An emulsifying chemical must be added to the mud to prevent water from escaping the emulsion. Oil based mud have high cost and cause environmental pollution.

Gas base mud or gas drilling fluid is used when the well is very hard and its permeability is low. The use of this type of mud increases the drilling speed.

Drilling fluid cycle

According to the proposed drilling program, drilling fluid materials are used to make drilling mud or treat it. These materials are made on the drilling rig inside the mud storage tanks with a volume of 400 barrels. Drilling mud is directed into the well through pumps and drilling pipes. After entering the well, the mud enters the daliz (distance between the well wall and the drilling pipes) through the drill bits and from there, mud goes to the shale shakers through the flow line pipe. Usually two or three shale shakers are used to restrain large drilling cuttings. Upon which, in order to get the solids with a smaller size, the drilling mud enters the solids control devices. After filtering, the cleaned mud enters the middle tank and from there re-enters the suction tank to be reused. This cycle continues during the drilling operation. The following figure shows the drilling fluid cycle.

Drilling fluid Production

Drilling fluids is a mixture of different chemicals and is stored on-site in drilling mud tanks. Various chemicals are added to the drilling fluid production process based on the application, from the tanks or from a special place shown in the figure below.

The most common types of drilling mud are described in this section:

  • Bentonite mud is usually used in development wells under normal drilling conditions or in the initial holes (aka top holes). To make Bentonite muds, Fresh water (water with a salt content below 10,000 PPM), Soda, Bentonite, and Caustic or lime, are commonly used.
  • .Water base heavy mud according to the required weight, can include saturated salt water, Light Soda Ash, starch, Barite and lime.
  • Oil based mud according to drilling mud program usually include diesel, control materials, primary emulsifier, lime, Calcium Chloride solution, secondary emulsifier, viscous materials and weight gain materials. Making an oil-based drilling mud usually takes 5 to 6 hours.
  • Emulsion mud is used in areas where water cannot be used due to high hydrostatics. Emulsion mud is a mixture of 70% diesel and 30% water with a type of emulsion fire called drilling mud emulsifier. Other drilling fluid materials are also used based on the type of application and drilling mud program (type of mud, weight of mud, etc.).

Environmental considerations of drilling fluid consumption

Environmental considerations of Drilling fluid consumption is one of the most important parts of the green drilling fluid supply chain. In this section, important considerations are expressed in this regard:

  • Ensure that bags and barrels are safe before unloading.
  • When unloading bagged materials, be careful that unloading operations are performed correctly. This is important in order not to prevent the material from spreading to the environment and causing contamination.
  • Open and use the material from the points created on the bags.
  • When using materials in the form of barrels, be careful not to damage the barrels spreading in the environment. If this happens, the spilled material should be cleaned immediately.
  • Before using this materials, barrels and bags should be correctly stored in a safe place and in compliance with environmental issues.
  • After using the materials, arrange empty barrels and bags regularly and prevent them from spreading in the environment.

Control Classification of drilling solids

Solids always make up the bulk of drilling fluids. Many of the properties of drilling fluids are achieved through the conscious use of solid additives. But the presence of excess solids in the fluid system is a major problem and causes great economic losses. However, these losses become apparent over time and their effect may not be immediately apparent.

The type and amount of solids in the drilling fluid system is a very important parameter in creating the properties of the drilling fluid system. These properties include density, viscosity, jelly strength, and etc. Excess solids in the drilling fluid system have a negative effect on parameters such as drilling speed, hydraulic status, torque, pipe jamming etc.

Classification of drilling solids

Solids are generally classified based on the following properties: • By size
• Based on the surface activity of solids
• Based on types of entrance to the system
• Based on specific gravity

Types of particlesSize (micron)Grouping
Bentonite, clay, ultra-fine solids<2Colloidal
Barite, silt, fine drilling solids2-74silt
Sand, drilling solids74-2000Sand
Solid drilling, sand>2000Sand

Another classification of solids is based on their surface activity. Solids are classified into two categories based on surface activity: active solids and inert solids. Active solids are solids that have a strong tendency to react with themselves and their environment and cause changes in the environment. Inert solids have very little tendency to react with themselves and their environment.

Solids are also divided into two categories in terms of how they enter the system. Some solids are added to the system as an additive for a specific reason. These solids create a special property in the system. Weighing materials, bentonite are in this category.

On the other hand, drilled solid and undesirable solid are solids that are added to the system during drilling. The main purpose of solids separation is to reduce the amount of these solids from the system. Drilling solids are divided into two general categories in terms of specific gravity: low-gravity solid and high-gravity solid.

Solids control methods

In Green drilling fluid supply chain management, control and separation of solids are divided into four general types:

  • Dilution
  • Gravity settling
  • Chemical separation
  • Mechanical separation

Dilution is any process in which the concentration of drilled solids in a system is reduced by adding a fluid to the drilling fluid.

In the separation of solids by gravity, when the fluid is left stationary for a period of time, larger solids settle to the bottom of the tank. As the density of the fluid increases, the time required for solids to settle increases due to the increase in floating power. In some cases, the size of the solids is so small that it would be difficult or impossible to separate them with the available equipment. In these conditions, the use of agglomerating chemicals can bring solids closer together and facilitate the separation of solids.

Mechanical separation of drilling solids

Mechanical separation is also based on screening, centrifuging and the use of vibrating motions. In the screening method, the physical separation of solids is based on size. The centrifuge created in the devices also causes the separation of solids from the fluid in opposition to the force of gravity. Vibrating motions will also help to separate solids. Especially in shale shaker, the combination of screening and vibration has a major effect on the separation of solids.

The drilling industry uses a lot of mechanical equipment, some of which are effective in separating solids from the system. Common mechanical equipment in the control of solids include shale shaker, hydrocyclones, centrifuge. Although Degasser is not a solid equipment control device, its use will increase the efficiency of other separation equipment.

Oil-based mud alternatives to reduce environmental impact

Oil based mud for drilling has advantages such as shale stabilization, high temperature resistance, drilling of salt layers, use during core extraction operations, high lubrication, corrosion control of metals and reusability.

The main disadvantage of using this mud is severe damage to the environment if it is not controlled. For this reason, we must look for alternatives in the drilling process.

Some of the disadvantages of oil-based mud that have led drilling experts to look for alternatives are:• Numerous environmental problems due to waste disposal and disposal of the system itself as well as the need for special equipment to control system pollution.

  • Very high initial cost to make oily fluids
  • High risk of fire due to low oil flash point and high steam pressure
  • Severe damage to oil fluids to the rubber parts of the fluid circulation system.

One way to remove oily fluids from the drilling process and reduce its environmental damage is to use synthetic base fluids.

Synthetic based mud

The environmental problems of oil-based mud and the enactment of heavy environmental deterrents led to the spread of other oily fluids. These types of mud are usually distinguished from ordinary oil-based fluids by the name of artificial base mud. Today, the term oily base fluids is considered more synonymous with this category of fluids.

In 1990, for the first time in the Norwegian part of the North Sea, artificial base mud were used for drilling. In 1991, the first well with artificial based mud was drilled in the English part of the North Sea. After this successful experiment, synthetic fluids received widespread attention. In the production of synthetic fluids, linear alpha olifins, olifin isomers, esters and ethers are used. The main disadvantages of synthetic fluids are the high cost of preparation and their low heat tolerance.

Glycol mud system

Glycol mud system consists of Drilling glycol, salt compounds such as Potassium Chloride and various polymers that provide suitable rheological characteristics during drilling. The main difference between this type of system and conventional water-based systems is the presence of Glycols. Glycol in the mud separates from the solution and forms a coating on the well. Therefore, by preventing water from coming into contact with the shale, it stabilizes the wall and prevents the destruction of the shale.

The advantages of the Glycolic system include the following:

  • Effective protection of shale layers
  • No use of petroleum based materials (the main volume is water)
  • Good lubricating power
  • Need little time to make and optimize mud
  • Less cost than oil mud
  • Has environmentally friendly additives such as starch, oxymers and…

Disadvantages of the glycol system include the following:

  • Requires a lot of care
  • Sensitivity to increased hardness, especially magnesium
  • Need equipped laboratory
  • Impossibility to use this mud in weights lower than water