GB2246802A

GB2246802A - Drilling fluids

Info

Publication number: GB2246802A
Application number: GB9116840A
Authority: GB
Inventors: Dennis Colin Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-06
Filing date: 1991-08-05
Publication date: 1992-02-12
Anticipated expiration: 2011-08-05
Also published as: GB2246802B; GB9017212D0; GB9116840D0

Abstract

A drilling mud comprises fish oil optionally in combination with other oils such as mineral oils and other drilling mud components such as gelling agents, e.g. bentonite, and weighting agents, e.g. barite. Water-based and oil-based fish oil containing muds are described.

Description

DRILLING FLUIDS The present invention relates to the use of fish oils in drilling fluids, for instance oil-based and water-based drilling muds comprising fish oils.

Drilling muds are multi functional fluids or slurries which are essential components in the process of drilling or boring wells to various depths.

A drilling mud will generally comprise an oil, water, at least one gelling agent and at least one emulsifying agent or surfactant. Drilling muds serve the many requirements of the drill head and in order to do so effectively they are formulated from many different components, the quantity and composition of the drilling mud being decided by the conditions likely to be experienced at the drill head. The drill head requires lubrication, cooling, actuation by an hydraulic fluid and the removal of cuttings away from the cutting surface and their transport to the well head. Drilling muds are generally of two types, oil-based and water-based depending on the percentage by weight content of oil. The oil serves to lubricate the cutting surfaces and moving parts of the drill head. Hydrocarbon mineral base oils are generally used.

A problem with mineral oils is that unless they are extensively refined then they contain many compounds which are toxic, e.g. to marine organisms. Legislation to counter the use of toxic drilling muds at sea has encouraged the development of lower toxicity drilling oils which for example meet the requirements laid down by the UK Department of Energy. Examples of these low toxicity drilling oils are Clairsols 430, 440, 530, 350M, 350MHF and TR4 produced by Carless. Despite the refining of mineral oils to produce such low toxicity drilling oils, these oils still exhibit some toxicity against marine organisms. The programme of anti-pollution legislation will set even lower toxicity limits in the future, and so the lifetime of the existing low toxicity oils is limited.New even lower toxicity drilling oils now need to be found which can be used in the formulation of drilling muds.

British Patent Specification No. 591825 discloses an oil-based drilling mud containing a soap formed by the insitu reaction of an alkali metal silicate and a fatty acid, which may be fish oil. The quantity of fatty acid used is small and neither the presence of free fish oil nor any function to be fulfilled by free fish oil is disclosed.

Rather, the function of the fatty acid added is to form a soap so that the fatty acid is no longer present but is consumed. The drilling muds disclosed are essentially water free, the only water content deriving from the water present in commercial sodium silicate solutions.

The present invention provides a drilling mud comprising a fish oil. It is known that most oils derived from living organisms are non-toxic to other organisms. In particular, fish oil is demonstrably non-toxic to fish and even promotes their growth. Drilling muds may be formulated using fish oil as the sole oil component.

However, the stability of fish oils in response to temperature and pressure is limited and such drilling muds may be restricted in their use to drilling shallow, low temperature wells or water bore holes. We have found.that these limitations of fish oils as base oils in most oil-based drilling muds can be overcome by blending them with low toxicity drilling oils. Stable emulsions can be formed when fish oils are mixed with low toxicity drilling oils and these blends can be used advantageously in the formulation of drilling muds of much lower toxicity than drilling muds formulated without the use of fish oils. A further advantage of using fish oils rather than hydrocarbon mineral oils in drilling muds is that the fish oils are more rapidly degraded by marine microorganisms.

In an alternative aspect the invention includes a drilling mud comprising fish oil (as hereinbefore defined) in the absence of sufficient basic silicate to saponify the fish oil and preferably in the absence of sufficient basic silicate to saponify a significant amount of the fish oil present, e.g. insufficient to saponify 30%, or more preferably 20 or even 10% or less of the fish oil. Basic silicates are preferably entirely absent. Preferably, other materials which form soaps with fish oils are similarly absent.

The term "fish oil" is used herein to mean an oil extracted from any species or mixture of species of fish and in addition to include whale oils.

Such a drilling mud may further comprise a mineral base oil. The mineral base oil is blended with fish oil so that the toxicity of the drilling mud is reduced compared to a drilling mud containing hydrocarbon mineral based oil but lacking added fish oil. The known toxicity of currently available hydrocarbon mineral base oils is ameliorated by the substitution of fish oils.

Commercial fish oils are manufactured from a variety of fish species and generally have common properties. The numbers and kinds of species of fish used to produce a particular batch of oil are dependent on the catch of fish bought into port. Although many commercially available fish oils are blends of fish oils obtained from different species, some oils such as capelin oil are derived from a single species.

Fish oil may be produced either from fish which is not used for human consumption such as sand eel or capelin, or as a by-product of fish processed for human consumption such as waste from smoked mackerel fillets.

Typically the whole fish and fish waste is treated in continuous processing machinery, which cooks, sterilises and presses the fish. The liquor is decanted and centrifuged to produce a crude fish oil.

The crude oil is then washed, refined, sometimes deodorised, sometimes winterised, polished and stabilised.

Oils from different species have different fatty acid compositions.

The use of all kinds of fish oil falls within the scope of the present invention. Although whale oils are included, the use of fish oils other than whale oils is preferred. The fish oil itself may be mixed with one or more oils derived form other organisms, marine or terrestrial.

The viscosity of hydrocarbon drilling oils now used in the formulation of drilling muds is usually in the range 2 to 5 centistokes. The blending of fish oils with drilling oils of this viscosity range results in an oil blend of generally similar viscosity range. The proportion of fish oil used in the drilling mud is preferably from 0.1 to 100% w/w of the total oil content. Preferably the proportion of fish oil is from 5 to 30% w/w of the total oil content and most preferably from 8 to 20% w/w of the total oil content, eg from 10 to 15 w/w. The hydrocarbon mineral base oil used is preferably a kerosene base oil, already refined to eliminate many toxic components. For example, one of the range of drilling oils produced by Carless are suitable for drilling mud formulations in accordance with the present invention. The low toxicity drilling oil, already of reduced toxicity is blended with the fish oil so that a drilling mud may be formulated which has an even lower toxicity than if the same quantity of just neat, refined mineral oil were used.

Known drilling mud formulations generally comprise both solid and liquid components. Oil, water and emulsifiers or surfactants comprise the liquid components.

Gelling agents and weighting agents comprise the solid components.

The drilling mud may comprise oil in an amount from 1 to 99% w/w of total liquid in said drilling mud.

Preferably the amount of oil in said drilling mud is from 5 to 958 w/w of total liquid in said drilling mud,and most preferably the amount of oil in said drilling mud is from 15 to 95% w/w of total liquid in said drilling mud, eg 20 to 80% w/w. The balance of the total liquid in the drilling mud may be made up of water and emulsifiers or surfactants.

The drilling mud may further comprise from 1 to 99% of water by weight of total liquid in said drilling mud.

Preferably the drilling mud comprises from 1 to 85% of water by weight of total liquid in said drilling mud, and most preferably the drilling mud comprises from 3 to 80% of water by weight of total liquid in said drilling mud, eg from 5 to 75% w/w of liquid, more particularly 10 to 65% w/w. Preferably at least 10%, more preferably at least 30% of water is present. In some preferred muds according to the invention, at least 50% or even at least 70% of water is present. Water based muds may contain up to 15% of oil based on the total liquid content. The balance of the total liquid in the drilling mud may be made up of oil and emulsifiers or surfactants.

The drilling mud preferably further comprises at least one emulsifying agent or surfactant. The inclusion of emulsifying agents or surfactants helps to generate an oil-water emulsion or dispersion. Commonly used agents include naphthenates, sulphonates and ethoxylated derivatives thereof, fatty acid amide derivatives, imidazolines and phenol ethylene oxide condensates.

Preferred surfactants or emulsifiers include Ethyl an HA, Ethyl an KEO and Ethyl an 44 which are products of the Harcross Chemical Group.

The drilling mud may comprise emulsifier or surfactant in an amount from 1 to 30% w/w of total liquid in said mud.

Preferably the drilling mud comprises emulsifier or surfactant in an amount from 1 to 15% w/w of total liquid in said mud and most preferably the drilling mud comprises emulsifier or surfactant in an amount from 2 to 10% w/w of total liquid in said mud. The balance of the total liquid in the drilling mud is therefore made up of oil and water.

The drilling mud of the present invention preferably further comprises at least one weighting agent. These additives act to increase the density of water-based drilling muds. Commonly used agents include barite (BaS04), iron oxide (Fe203), galena (PbS) or calcium carbonate (CaCO3). Soluble salts or mixtures of soluble salts may also be used as weighting agents, for example sodium chloride (NaCl), calcium chloride (CaCl2) or a mixture of calcium chloride and calcium bromide (CaCl2/CaBr). The weighting agents listed above may be used singly or in any combination.

The drilling mud preferably contains at least one gelling agent. This may be bentonite (montmorillonite) with the generally known formula 0.33Na(All 07MgO 3303) 0.4Si2.H20.

The emulsifier or surfactant component may be formulated or selected to confer on the drilling mud a required level of temperature and/or pressure stability.

The drilling mud in accordance with the present invention may contain fish oil modified by refining and/or chemical treatment prior to its use in said drilling mud.

The fish oil is preferably winterised to ensure working viscosity at low temperatures.

The use of fish oil is not limited to any one particular formulation of drilling mud. Aqueous- and mineral oil-based drilling muds are included within the scope of the present invention. Some of the kinds of aqueous-based drilling muds commonly included are bentonite muds, phosphate muds, gel-chemical muds, lignite and lignosulphate muds, calcium muds, low solid/non-dispersed polymer muds and salt muds. Some of the mineral oil-based drilling muds included are true oil-based muds, invert emulsion muds and low oil content muds.

The present invention also provides in a second aspect a drilling oil blend for use in the formulation of drilling muds comprising mineral oil blended with fish oil. Rather than supplying a ready formulated drilling mud it may be advantageous to supply a drilling oil comprising hydrocarbon mineral base oil blended with fish oil.

The present invention further includes the use down hole in a drilling or boring process of a drilling fluid comprising a fish oil. A drilling fluid in which fish oil in the sole or a major component may be used by way of example in accordance with this aspect of the present invention in drilling shallow, low temperature wells. An example of such a well would be a bore hole made for water.

The lubricating and non-toxic properties of the fish oil could be used advantageously in the drilling of water bore hole where a complex drilling mud formulation would not be desired or necessary. The fish oil would simply act as a lubricant and coolant to aid the cutting action of the drill head.

The present invention will now be illustrated by means of the following examples: EXAMPLE I A typical batch of commercially available fish oil, such as Winterised Fish Body Oil for use in the formulation of drilling muds formulated to provide an embodiment of the present invention may have the following properties: VISCOSITY (Cs): Viscosity at 20"C: 60-9Omm2/sec Viscosity at 50"C: 20-30mm2/sec Viscosity at 90 : approx lOmm2/sec DENSITY: Density at 15"C: approx 0.92kg/l FREE FATTY ACIDITY: 0.5% w/w max, as oleic acid UNSAPONIFIABLE MATTER: 2.5 w/w, max SAPONIFICATION VALUE: 180-190 mg KOH/g COLOUR: Colourless to pale yellow EXAMPLE II An oil-based formulation of the True Oil Base type of drilling mud formulated to provide an embodiment of the present invention where the weight of fish oil used is 16.9% of the total weight of oil contained in the drilling mud. Weights of the various components forming the mud are given in kg.

Clairsol 350 (hydrocarbon oil) 171.7 kg Fish oil 35.0 kg Ethylan HA 3.18 kg Ethylan KEO (emulsifier) 2.27 kg Ethylan 44 2.27 kg Water 13.4 kg Barite (weighting agent 117.5 kg Bentonite (gelling agent) 4.54 kg EXAMPLE III An oil based formulation of the Invert-type of drilling mud formulated to provide an embodiment of the present invention where the weight of fish oil used is 14.2% of the total weight of oil contained in the drilling mud.

Clairsol 350M (hydrocarbon oil) 86.5 kg Fish Oil 14.3 kg Ethylan HA 3.18 kg Ethylan KEO (emulsifier) 2.27 kg Ethylan 44 2.27 kg Water 152.0 kg Barite (weighting agent) 93.4 kg Bentonite (gelling agent) 2.27 kg EXAMPLE IV An oil based formulation of the Low Oil Content-type of drilling mud formulated to provide an embodiment of the present invention where the weight of fish oil used is 11.4% of the total weight of oil contained in the drilling mud.

Fish Oil 4.79 kg Clairsol 350M (hydrocarbon oil) 37.4 kg Ethylan HA 4.54 kg Ethylan KEO (emulsifier) 4.54 kg Ethylan 44 4.54 kg Water 209.1 kg Barite (weighting agent) 104.8 kg Bentonite (gelling agent) 4.54 kg EXAMPLE V An oil-based formulation of the Low Oil Content-type of drilling mud formulated to provide an embodiment of the present invention where the weight of fish oil used is 100% of the total weight of oil contained in the drilling mud.

Fish oil 74.3 kg Ethylan HA 4.54 kg Ethylan KEO (emulsifier) 4.54 kg Ethylan 44 4.54 kg Water 188.7 kg Barite (weighting agent) 93.4 kg Bentonite (gelling agent) 2.72 kg EXAMPLE VI A water-based formulation of drilling mud according to the invention has the following composition.

Fresh water 138 litres (0.87bbl) Bentonite (prehydrated) 1 1 kg (251b) Lignosulphonate 1 kg (2.61b) NaOH 0.9 kg (21b) Barite 87 kg (191lb) Drilled solids 18 kg (401b) Fish oil 24 kg (15%) EXAMPLE VII A further water-based formulation which is a 12 ppg polymer mud has the following composition: Sea water 138 litres (0.87bbl) Bentonite (prehydrated) 2.3 kg (51b) Xanthan gum 0.45 kg (llb) PHPA polymer 0.7 kg (1.51b) Low viscosity PAC 0.9 kg (21b) Barite 80 kg (1781b) Drilled solids 18 kg (401b) Fish oil 17 kg (10 approx)

Claims

CLAIMS 1. A drilling mud comprising fish oil as hereinbefore defined.
2. A drilling mud as claimed in Claim 1, wherein said drilling mud further comprises a mineral base oil.
3. A drilling mud as claimed in Claim 2, wherein the proportion of fish oil is from 0.1 to 100% w/w of the total oil content.
4. A drilling mud as claimed in Claim 3, wherein the proportion of fish oil is from 5 to 30% w/w of the total oil content.
5. A drilling mud as claimed in Claim 4, wherein the proportion of fish oil is from 8 to 20t w/w of the total oil content.
6. A drilling mud as claimed in any one of Claims 1 to 5, wherein the amount of oil in said drilling mud is from 1 to 99%w/w of total liquid in said drilling mud.
7. A drilling mud as claimed in Claim 6, wherein the amount of oil in said drilling mud is from 5 to 95% w/w of total liquid in said drilling mud.
8. A drilling mud as claimed in Claim 7, wherein the amount of oil in said drilling mud is from 15 to 95% w/w of total liquid in said drilling mud.
9. A drilling mud as claimed in any one of Claims 1 to 8 further comprising from 1 to 99% of water by weight of total liquid in said drilling mud.
10. A drilling mud as claimed in Claim 9, comprising from 1 to 85% of water by weight of total liquid in said drilling mud.
11. A drilling mud as claimed in Claim 10, comprising from 3 to 80% of water by weight of total liquid in said drilling mud.
12. A drilling mud as claimed in any one of Claims 1 to 8, comprising at least 10% water by weight based upon the total liquid in said mud.
13. A drilling mud as claimed in Claim 12, comprising at least 30* water by weight based upon the total liquid in said mud.
14. A drilling mud as claimed in Claim 1, wherein said fish oil is other than whale oil.
15. A drilling mud as claimed in any preceding claim, wherein said drilling mud further comprises at least one weighting agent.
16. A drilling mud as claimed in any preceding claim, wherein said drilling mud further comprises at least one emulsifying agent or surfactant.
17. A drilling mud as claimed in any preceding claim, wherein said drilling mud contains at least one gelling agent.
18. A drilling mud as claimed in any preceding claim, wherein said drilling mud further comprises at least one temperature and/or pressure resistance additive.
19. A drilling mud as claimed in any preceding claim, wherein said fish oil is modified by refining and/or chemical treatment prior to its use in the drilling mud.
20. A drilling mud as claimed in Claim 1, wherein the drilling mud is free from basic silicates or contains insufficient basic silicate to saponify more than 30% of the fish oil.
21. A drilling mud substantially as hereinbefore described in any one of Examples II to W/,
22. A drilling oil blend for use in the formulation of drilling muds comprising mineral oil blended with fish oil.
23. The use down hole in a drilling or boring process of a drilling fluid comprising a fish oil.