What types of plugging materials are driving the well plugging and abandonment market?

Plugging and abandonment closes oil/gas wells permanently using abandonment techniques and plugging materials, ensuring environmental safety.The purpose behind the permanent abandonment is to inhibit crossflow or pressure buildup in the wells and their surroundings. By isolating all penetrable water zones and hydrocarbon zones of different pressure regimes from one another and the seabed. Well plugging and abandonment in decommissioning is vital; improper sealing can pose environmental threats, emphasizing its significance in projects. Several types of plugging materials and abandonment strategies are available in the well plugging and abandonment market to ensure superior abandonment.

Types of materials:

The plugging and abandonment process requires different types of materials according to the distinct requirements and conditions of the wells. A description of a few of these materials is given below:

Portland cement: Portland cement is the most used plugging material globally. It mainly consists of calcium hydroxide and several calcium silicate phases.Addition of specific additives allows a wide range of various specialized types of cement systems like flexible cement and expandable cement.

Blast furnace slag (BFS): BFS is a by-product of steel production during the operation of a blast furnace, and it is mounted on top of the molten iron in furnace, and contains silica, lime, alumina, and magnesia.Depending on the cooling process, this slag product can be utilized as a hydraulic binder material, equally by itself as an additive in cement or directly in well cementing applications.

Low melting point metal alloys: Metals with low melting points have been tested for reducing sustained casing pressures both in the existence of water-based and oil-based drilling fluids.Also, in the composition of low melting eutectic metal plug, one of the materials was bismuth. This is beneficial for the high-quality bonding of wells and pipe surfaces, as this metal extends significantly on solidification, thus building a good metal-to-metal bond.Bismuth alloys have been recently used as plugging material in permanent plugging and abandonment due to their superior bonding benefits.

Bentonite: Concentrated bentonite has been used as a material for plugging and abandonment of oil and gas wells owing to its ability to expand and low permeability.In recent years this material has been tested and successfully used for plugging and abandonment operations in several wells in Australia and US.According to laboratory tests, it has been seen that concentrated bentonite would re-heal itself in the case of cracks occurring.

Thermosetting polymers (resins): Thermosetting polymers are particle-less fluids which solidates into an impermeable material on curing.The curing is a temperature-activated process and appears at a predefined temperature. Additionally, density and viscosity can be modified for different applications by the combination of particles.Resins have been applied as plugging materials both in the Mexican Gulf and Noth Sea. Concerning durability, laboratory tests have displayed a loss of strength in downhole environments like crude oil and H2S.Other applications of resins are squeeze procedures in the annulus between two casings to repair casing leaks and regain zonal isolation.

Unconsolidated sand slurries: Sand slurries have been used for well plugging and abandonment and the permeability should be theoretically less than 0.01 mDarcy.

If a system with exclusively monodisperse particles was utilized, maximum proportion of sand concentration would be just a bit more than 50%, leaving remained to a permeable pore volume.Sand slurry was developed and qualified for temporary abandonment due to its easily removable and non-setting nature.

Geopolymers: Geopolymers are rock-like and inorganic materials, which can be denoted as artificial stone. These are alkali-activated materials with less calcium content.They are based on different raw materials like kaolinite, fly ash, and several types of rocks. Geopolymers were developed and utilized as construction materials in civil engineering.They have not been used in plugging operations or other well applications.Research indicates potential of certain cements for well plugging due to low permeability, shrinkage, high temperature stability, strength, and contamination tolerance.

Therma Set: Therma set is a well plugging material and an alternative to cement, which was developed to overcome traditional cement issues.It is defined as a particle free polymer-based material produced by Wellcem AS. It is pumped in the form of liquid and transforms into solid form by a temperature-activated process.The initialization of curing process, which refers to the solidification of Therma Set material is activated by downhole temperatures.Then the curing agent can be developed to fit the predefined temperatures of an area where plug will be inserted.