Patent Application
20160304398
The invention relates to a material for use in subterranean wells. More specifically the invention relates to a material for sealing hydrocarbon wells, wherein the material is comprised of a hydraulic cement and a prepolymer.
During the lifetime of oil and gas wells, situations arise where there is a need for the introduction of a material with sealing properties. Such situations include plugging and abandonment (P&A), lost circulation, and isolation of zones in the well. Plugging and abandonment operations are generally carried out in situations where the well does not produce enough hydrocarbons to be profitable, or in situations where the well has neared the end of its lifetime and is depleted of hydrocarbons. Temporary plugging of wells is typically carried out during maintenance operations of the well. Lost circulation describes the situation where drilling fluid is lost in the formation and flows into the formation instead of returning through the annulus and to the surface. Zonal isolation is carried out to prevent the cross-flow of fluids between geological layers and to reduce the volume of produced water.
In the prior art, cement is commonly used as a sealant material. The disadvantages connected to the use of ordinary cement is long setting time, insufficient mechanical properties for certain applications, poor penetration capability in formations, susceptibility to cracking, and poor resistance towards certain chemicals, in particular acids. There is a need in the art for a material that can improve the properties of ordinary cement for the purposes mentioned herein.
The applicant has previously patented a technology (U.S. Pat. No. 6,082,456, NO310941B1) that seeks to overcome many of the disadvantages exhibited by the use of cement as a sealant material in oil and gas wells. The material described in the patents comprises a prepolymer, at least one vinylic monomer, an initiator, an inhibitor and optionally, a filler, hereafter described as “the prepolymer mixture”. The prepolymer is in the form of at least a partially unsaturated polyester or epoxy vinylester. The material described in the referred patents is particularly advantageous compared to cement with respect to its short setting time.
The invention seeks to provide a new material with sealant properties for the use in oil and gas wells. It has been discovered that the prepolymer mixture claimed in the applicants patent combined with ordinary cement, surprisingly yields a material with several beneficial properties compared to the use of cement alone. When the prepolymer mixture was blended with fresh cement, it was found that the material resulting from the combination exhibited one or more the following properties:
Controllable and shorter setting time compared to ordinary cement.
Better mechanical properties of the material compared to ordinary cement (higher compressive and tensile strength, better elongation properties, and lower Young's modulus).
Beneficial properties obtained even at a low ratio of polymer/cement (10 weight % polymer or less), wherein the polymer acts as a plasticity enhancing additive for cement.
Enhanced thermal resistance compared to the neat polymer.
Increased chemical resistance of cement. The polymer acts as a barrier towards chemical exposure of the cement.
After curing, the material possesses much lower permeability relative to ordinary cement.
Japanese patent application JPH02286781 describes an agent for preventing loss of circulating drilling mud. The agent is comprised of a thermosetting resin and, a hydraulic silicate material and emulsifier. The hydraulic silicate material can for example comprise Portland cement. The disadvantage of the described agent is the lack of control over setting time.
The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.
The object is achieved through features which are specified in the description below and in the claims that follow.
In a first aspect the invention relates to method in accordance with claim 1.
The inhibitor of the composition used in the method can comprise p-benzoquinone.
The composition can further comprise an accelerator. The accelerator can comprise a compound, wherein the compound can be selected from the group including inorganic salts, transition metal compounds, inorganic hydroxides amides, amines and aromatic compounds. The aromatic compound can further comprise N,N-dimethyl-p-toluidine.
The prepolymer can comprise a curable material, wherein the curable material is selected from the group including unsaturated polyesters and epoxy vinyl esters.
The monomer can comprise an unsaturated compound, wherein the unsaturated compound is selected from a group including vinyl-, allyl- and acrylate compounds. The vinyl compound can be selected from the group comprising styrene and vinyl toluene. The allyl compound can comprise diallylphtalate. The acrylate compounds can be selected from the group comprising 2-hydroxy ethyl methacrylate, 2-hydroxy propyl methacrylate and butanediol dimethacrylate.
The hydraulic material can comprise a hydratable material, where the hydratable material can be selected from the group including Portland cement, Portland blastfurnace cement, Portland flyash cement, Portland pozzolan cement, Portland silica fume cement, masonry cement, pozzolan-lime cements, supersulfated cements, calcium aluminate cements, phosphate cements and geopolymer cements, and gypsum.
The water can be present in an amount of 20 to 60 weight percent of the hydraulic material.
The prepolymer can be present in an amount of 10 to 90 weight percent of the total mass of the composition.
The free radical initiator can comprise a dissociable compound, wherein the dissociable compound can be selected from the group including peroxides and azo compounds. The peroxides can be selected from the group comprising tert-Butyl cumyl peroxide and dibenzoyl peroxide.
The composition can further comprise a setting inhibitor, wherein the setting inhibitor can be selected from the group including sucrose, tartaric acid, gluconic acid δ-lactone, lignosulfonates and organic phosphonic acids. The lignosulfonate can comprise calcium lignosulfonate.
The composition can further comprise a setting accelerator, wherein the setting accelerator can be selected from the group including chloride salts, carbonates, silicates, aluminates, nitrates, nitrites, sulfates, thiosulfates and hydroxides.
The composition can further comprise a dispersing agent.
The composition can further comprise a viscosifying agent.
The composition can further comprise a stabilizing agent.
The composition can further comprise a density modifying agent. The density modifying agent can selected from the group including glass beads, trimanganese tetroxide, calcium carbonate and barite.
In a second aspect the invention relates to use of a composition for sealing hydrocarbon wells in accordance with claim 25.
In the following it is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:
It should be noted that the below-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
In the following a series of experiments are described to illustrate preferred embodiments of the invention.
A first series of experiments (experiment 1 to 5, se
The prepolymer mixture (part A) was prepared by mixing prepolymer, radical initiator and optionally an inhibitor. The cement slurry (part B) was prepared by blending cement, water and optionally a setting time inhibitor. When part A and part B had been blended separately to achieve sufficient homogeneity, quantities of part A and part B were weighed in and part A and B were blended. The quantities of the components that were used are shown in table 1. All quantities are given in weight percent. The setting time and hardening time for each of the mixtures was recorded. The setting time was defined as the time from start of the reaction until appearance of the exothermic peak. The hardening time was defined as the time from start of the reaction until the exothermic peak returned to the baseline. In case of an unclear exothermic peak, the setting time was defined as the time from start of the reaction until the composition resisted flow by pouring.
It could be observed from experiment 1 through 3 that the reduction of the amount of initiator increased both the setting time and the hardening time, providing a means for controlling these parameters. Additional inclusion of an inhibitor and a cement hardening inhibitor in experiments 4-5 further increased the setting time and hardening time.
A second series of experiments (experiment 6-9, see
It could be observed from experiment 6-9 that increasing the amount of accelerator reduced both the setting time and the hardening time, providing an additional means for controlling these parameters.
A third series of experiments were carried out to determine the compressive strength of several blend ratios of prepolymer mixture and cement slurry (see
A significant advantage is gained from the ability to increase the compressive strength of pure cement by addition of the said prepolymer mixture. At even low levels of addition of the prepolymer mixture (20/80 prepolymer/cement ratio), the compressive strength of the cement was surprisingly found to be more than doubled compared to cement alone.
Furthermore, another significant advantage related to the invention is the ability to control the setting time and the hardening time of the composition by varying the amounts of initiator, accelerator and cement inhibitor. This allows for a precise tailoring of the composition to the relevant well conditions and placement times involved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20131607 | Dec 2013 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NO2014/050224 | 12/3/2014 | WO | 00 |
