Reducing the environmental impact of this section requires the analysis of complex issues that require a proper answer due to its direct relationship with the quality of human life.
The following are general answers to these questions:
- Identify waste generating activities
- Investigating the potential impact of waste generated on the environment
- Understanding the mechanisms and routes of waste transfer and the distribution of pollutants
- Study of effective ways in waste and pollutant management
- Applying purification methods to reduce the volume and toxicity of materials
- Optimization of evacuation methods
- Cleaning contaminated environments
Sources of drilling waste
In the upstream oil and gas industries, there are two major types of operations that can affect the environment. Drilling and exploitation, both of which bring significant amounts of waste into the environment. Measures to understand how to produce such waste and how to distribute it are among the main needs. With such knowledge and the use of methods to improve operations, the resulting damage can be minimized and even completely eliminated in some cases.
Excavation involves a series of operations in which a hole is made in the ground to direct underground hydrocarbons to the surface. An average of one hundred wells are used to drill each oil tank and several thousand barrels contaminated with various substances harmful to the environment are used to drill each well. These materials are released into the ground after use. Evidently, one of the main sources of environmental pollution in drilling operations is directly related to fluids and compounds that are used as drilling mud. In addition, large amounts of fragments of subsurface formations, saline water in the lower layers of the earth and petroleum hydrocarbons are transferred to the earth’s surface during this process.
The effect of drilling fluids on soil properties
Drilling fluid is a water or oil-based compound that, along with additives, plays effective roles in drilling operations. These include maintaining the pressure of the well and preventing it from erupting, maintaining the strength of the well wall (formation), transferring cuttings to the ground surface, cooling and lubrication of the drilling bit, etc. During drilling operations, the consumed and waste fluids along with other materials are transferred into large pits. At the end of the drilling process, the wells are left in the same way as before, often without a repair process.
Due to the direct contact of these materials with the soil, this environment undergoes chemical, physical and biological changes. Identifying the trend of these changes requires methods that can be used to better determine the distribution of these materials at spatial distances and determine the extent and scope of their effect.
in green drilling fluid supply chain management article we note Environmental considerations of drilling fluid consumption, please refer to this article for more details.
Discharge of drilling waste
The most common method for discharging drilling fluids involves directing these materials to the mud pits that are constructed in the vicinity of the drilling rig. The area of these pits can reach several thousand square meters depending on the duration of drilling and its type. These materials and chemicals remain in the pits and their volume will decrease over time due to infiltration into the subsoil or evaporation.
Such materials and chemicals are unloaded using the spraying method performed by tanker trucks. This method is one of the expensive methods that are used in areas where it is not possible to build drainage pits (especially in mountainous areas).
In this method, the tankers after unload their cargo after loading and during the distance while moving in a predetermined place. Re-injection of these materials into the underground layers is one of the appropriate methods to remove these contaminants. The re-injection process should be done taking into account the non-contamination of aquifers.
Environmental effects of drilling rigs
Drilling rigs are generally made of low density particles and in addition to causing environmental problems, generally have an adverse effect on the properties of drilling mud. Drilling mud and rigs are inevitable toxic by-products in drilling. Drilling rigs make up about 10% of the volume of drilling waste. During the drilling process, hazardous fluids and drilling rigs combine with oil, water and other chemicals to form a toxic drilling mix. This mixture contains toxic chemicals such as oil, phenol suspension solids, arsenic, chromium, cadmium, lead, mercury, natural radioactive materials and barium materials. These compounds vary depending on the location of the well, the depth of the well and the type of used drilling fluids and cement.
The amount of solid drilling cuts decreases as the diameter of the well decreases. Drilling rigs that are the result of drilling operations for oil and gas wells contain large amounts of drilling mud that contain oil compounds and are harmful to the environment. Some of these damages include disruption of the soil’s biological activities, toxic effects on plants, and harmful effects on humans due to the entry of substances into the food chain.
Environmental effects of heavy metals in drilling mud
Heavy metals enter drilling fluids in two ways. Many metals are naturally present at the drilling site and therefore enter the fluid used during drilling. Some metals are added to the drilling mud as an additive to create the desired properties. For example, Barium and Mercury in Barite as a density controller are sources of heavy metals in crude oil drilling fluid. Crude oil naturally contains very different concentrations of different metals. Metals in crude oil include: aluminum, calcium, chromium cobalt, copper, gold, iron, lead, magnesium, manganese, nickel, phosphorus, platinum, silicon, silver, sodium, strontium, uranium, tin and boron. Nickel and vanadium have the highest concentrations.
| NO. | Heavy metals | Environmental effects on human health |
| 1 | Arsenic | Weakness, anorexia, bronchitis, periodic neurological diseases, skin diseases, gastrointestinal problems and damage to the liver, heart, nerves and kidneys |
| 2 | Mercury | Weakness, fatigue, anorexia and indigestion, severe tremors in severe high-level contacts |
| 3 | Barium | Barium ion in some cases causes stroke and paralysis in living organisms |
| 4 | Cadmium | Kidney damage, bone cracks, kidney stones, osteoporosis, shortness of breath and pain in the head and joints |
| 5 | Chromium | Severe irritation of the respiratory system, respiratory problems and kidney damage |
| 6 | Cobalt | At high concentrations it causes inflammation, damage to the heart and digestive system, as well as damage to the liver and kidneys. |
| 7 | Lead | Brain injury, seizures, mental disorders and death |
| 8 | Nickel | skin allergies and allergic reactions |
| 9 | Vanadium | Effect on eyes and respiratory system in more severe contact Damage to lung, liver, kidneys and heart |
| 10 | Zinc | Harmful effects of high concentrations on the lungs |
Waste management
In order to protect the environment and the ecosystem, the environment must be prevented from being polluted. The first step to achieving this is to prevent the production of pollution as much as possible. In some industrial activities such as drilling, pollution is inevitable. In such cases, one should minimize the amount and try to recycle or reuse it. In cases where these environmental activities cannot be implemented, these wastes will inevitably enter the environment.
To reduce the amount of pollution, wastes must be refined, and wastes that do not cause significant damage to the environment are discharged into the environment (environmental standards and regulations determine whether the pollution is harmful). Contaminating waste is either eliminated by chemical or biochemical processes or inevitably buried, which must be done with the utmost care in accordance with the standard. This section discusses the four activities in order to protect the environment and comply with environmental laws.
Prevention of waste generation
The easiest way to protect the environment is to prevent the formation of contaminating waste, which is achieved by reducing the volume or amount of pollution. For this purpose, the following measures are provided:
Replacement of process and products that can reduce the volume and amount of waste contamination. Modify the process and use more efficient mechanical equipment, improve drilling techniques such as the using effective drills to reduce the use of chemical additives and ultimately reduce pollution.
– Complete consumption of chemicals and return unused materials to the seller.
Revival & Recycling
After examining the ways to reduce contaminants, in this stage, strategies for recycling and reuse of waste will be studied.
- Return to process and reuse
- If possible, burn to produce energy
- Reuse in other processes or recycling to reuse in other industries
Treatment of drilling fluids wastewater
Due to the destructive and long-term effects of drilling wastes into the sea and their negative effects on marine ecosystems, governments, industries and organizations working on the environment are looking for ways to reduce the volume of drilling effluents. One method of this is to re-inject the effluents into the seabed or, if possible, to treat them. In 1995, the American Petroleum Institute explored various methods for treating drilling wastes. In the published reports, the pollutants that affect the toxicity of the waste were announced as follows:
Very fine suspended particles, salinity above 90%, volatile compounds, extractable organic matter, ammonia solution and vapors and hydrogen sulfide.
In API reports, reducing effluent pollution to an acceptable level through a combination of different methods has been proposed. In choosing the wastewater treatment method, cost estimation is necessary and is one of the influential factors in determining the treatment method. Table 3 shows the different methods of treatment of drilling effluents.