ES2573879A1 - Procedure for solidification of a water-based drilling fluid in hydrocarbon wells - Google Patents

Abstract

Procedure for the solidification of a water-based drilling fluid in hydrocarbon wells, for application in the cementing of the mentioned wells at temperatures below 383 k, by means of the conversion in cementing mud of a drilling fluid based on brackish water with lignosulfonate with the addition of a byproduct of steelmaking called iron-poor electric arc slag (<25%) as a hydraulic material. Said slag must be basic, granular and amorphous in character, in addition to complying with the requirements of astm specification c-989-99. (Machine-translation by Google Translate, not legally binding)

Description

Procedure for solidification of a water-based drilling fluid in hydrocarbon wells.

OBJECT OF THE INVENTION

The present invention, as expressed in the statement of this specification, has as its object a process to convert the brackish water-based drilling fluid with lignosulfonate into one of its additives, at temperatures below 383 K, and using electric arc furnace slag poor in iron «25%), a byproduct of steel production, as hydraulic material. Said slag must be basic, granular and amorphous, in addition to complying with the requirements of the ASTM C-989-99 specification.

The scope of this invention would focus on the oil industry, obtaining a procedure for cementing hydrocarbon wells, economically, technically and environmentally favorable with respect to traditional technology.

BACKGROUND IN THE STATE OF THE TECHNIQUE

The cementing of hydrocarbon wells is carried out in order to successfully develop the extraction of natural gas and oil. This process is so important that the success of a hydrocarbon producing well will depend on its architecture and the way in which the well was completed or cemented. The cementation of a well has several objectives among which it is important to provide zonal insulation and protect the casing pipe from axial loads and corrosion. Likewise, the drilling mud was introduced along with the rotary drilling of hydrocarbon wells in 1901. Initially, the primary purpose of the drilling mud was to remove the rubble in a continuous way, but with the progress and technological advance of the rotary drilling , also increased the sophistication of the mud and with it its multiplicity of functions (Moore, "Drilling Practices Manua /", Tulsa: Penn Wel / Books; 1986). Therefore, drilling fluid is defined as that fluid

(usually water or oil based) whose properties have been modified by

commercial and / or native solids, dissolved and / or suspended.

The "conventional" method of cementing oil wells has been applied since the early twentieth century, being a process consisting of mixing dry cement, additives and water to form a grout that is pumped into the well through the coating string and place it in the annular space, between the hole and the outside of the casing. It is then allowed to set and harden in order to provide a barrier that prevents the migration of gas or other fluids present in the formation, as well as serving as a support for the pipe (Ne / son and Guillot, "Well cementing", 2nd Edition. Houston: Sch / umberger; 1990). The success of the cementation of a well, depends on a good planning and execution of the necessary works that allow to obtain a good zonal isolation.

The new oil and gas fields discovered in the world show the need to drill in more severe conditions, fields with high pressures and temperatures and difficult to access. Considering this trend, it is expected that in the coming years the use of unconventional drilling techniques will be necessary, including highly deviated wells and horizontal wells. For the exploitation of oil and gas fields to be economically viable, it is essential that all operations are carried out economically, requiring improvements in conventional drilling techniques and the introduction of new technologies, to cover the difficulties inherent in this scenario (Economides and others, Petro / eum well construction, New York: John Wiley &Sons; 1998).

Therefore, the efforts that oil companies have carried out in recent years are important in order to obtain cement slurries with adequate physical properties to withstand high temperature conditions. In fact, several cases of serious problems associated with cementation in wells are known, including loss of the well (Miranda et al., "S / ag cementing versus conventiona / cementing: Comparative bond resu / ts". Paper 39005 presented at the Fifth Latin American and Caribbean Petro / eum

Engineering Conference and Exhibition; 1997).

Currently, several technologies are available that are applied in the process of cementing oil and natural gas wells. An important part of the new technologies in cementing hydrocarbon wells are cementitious materials. It is about finding and being able to make use of materials that offer advantages in the control of the problems associated with the migration of gas, that in general ensure a better zonal isolation in the short and medium-long term and ultimately that offer advantages in the economy of the process in general. One of those materials is blast furnace slag, a material that has been shown to offer advantages in cementing operations over the use of Portland cement. Steel mill slags have been used for the manufacture of certain cements that are used in civil constructions where special conditions of compressive strength or environmental attacks are required (Tay / or, "Cement Chemistry", 2nd Edition. London: Thomas Telford;

1998).

Thus, since the 1990s, a new method of cementing wells has been implemented that has advantages over the conventional method. In fact, in 1991 the Shell company obtained a first US5058679A patent for "Cementing sludge", also known as "S-Mix" technology, whose fundamental ingredient is blast furnace slag. This technology involves the combination of drilling fluid, activators (can be chemical or thermal) and blast furnace slag which, as already mentioned, is a byproduct of steelmaking. The slag, so that it can be used in cement sludge technology, must be cooled quickly so that it has hydraulic properties. This technology shows advantages in the cementation of highly deviated wells because the cement sludges formed by a drilling and slag fluid offer excellent solids suspension, very low permeability and a free water value equal to zero (Nahm and others, "S / ag mix mud conversion cementing techn% gy: Reduction of mud disposa / vo / umes and management of rig-site drilling wastes ". Journa / of Petro / eum Science Engineering

11: 3-12; 1994).

Blast furnace slag is used in the conversion of drilling mud into cementitious material, suitable for use in hydrocarbon wells as a substitute for conventional cement slurries. Cowan et al. ("S / ag mix mud conversion techn% gy: Reduction of mud disposa / 5 vo / umes and management of rig-site dril / ing wastes". Paper 25988 presented at SPEIEPA Exp / orations & Production Enviromenta / Conference, San Antonio; 1992) state that the solidification of the mud has been pursued to improve the zonal isolation due to a better rheological compatibility between the cementing fluid and the mud, which contributes to a better displacement of the latter; low impact

In the contamination of the sludge and in the behavior of the properties thereof converted into cementitious material, as well as an improvement in the seal in the annular zone due to the potential solidification of the plaster and of any non-displaced sludge.

Publications in this regard show advantages of the technology of "Mud

15 cementing agent "in certain cementing operations of hydrocarbon wells (Javanmardi et al.," S / ag mud solidification techn% gy so / ves cementing prob / ems and reduces costs at Auger ". Oi / Gas Journa / 15: 49-57 ; 1993) These advantages are both technical, economic and environmental, however, one of the problems in the use of such cementitious material in the construction of wells is the supply of

20 same. Some cementing companies internationally offer slag as cementitious material; although its use is rare in cementing operations despite the advantages it offers in certain applications.

Cowan et al. (1992) also state that due to the low impact on

25 properties of the drilling fluid, slag can be added in low concentrations (approximately 100 gIl) during drilling operations. Both the plaster and the confined mud have the hydraulic material. After reaching the depth at which the casing pipe is to settle or fix, drilling mud is circulated containing the activators

30 chemicals and high concentrations of slag (1100 gIl) that will be used to cement the pipe. These activators, in turn, will activate any scum that is present in the plaster or in any mud not displaced, ensuring an effective seal in the annular zone, which allows us to have a "universal fluid", is

That is, it allows us to drill and cement at the same time.

By way of conclusion, the "Procedure for solidification of a water-based drilling fluid in hydrocarbon wells" consisting of the cementation of hydrocarbon wells at temperatures below 383 K, by conversion into cementitious sludge of a base drilling fluid water with the addition of a by-product of the manufacture of steel called iron arc slag poor in iron "25%), provides an alternative to the state of the art that improves conventional cementing processes, both technically and environmentally and economically.

Being especially useful for addressing very appropriate seals in the annular area of hydrocarbon wells by in situ solidification of the drilling fluid, in situations where the prevention of cement contamination by the drilling fluid is critical to the success of the operation , both in secondary cements and in plugs.

EXPLANATION OF THE INVENTION

By way of explanation of the invention, the "Procedure for the solidification of a water-based drilling fluid in hydrocarbon wells" consists in the cementation of hydrocarbon wells at temperatures below 383 K by the conversion into cementitious sludge of a fluid of water-based drilling with the addition of a byproduct of the steel manufacturing called iron arc slag poor in iron «25%).

As for the procedure itself, first of all the design of the cementitious sludge is very similar to the design process of a cementitious sludge with the "Smix" technology. The sludge can be made in the laboratory or if you are near the field, take a mud sample at one point during drilling. The brackish water-based drilling fluid with lignosulfonate was used to perform cement sludge testing, because it is a mud widely used in the oil industry. To be employed in this technology you must comply with the parameters of this mud.

With respect to the use of amorphous and basic slag from an electric arc furnace poor in iron «25%), it is a non-metallic product consisting essentially of calcium silicates and aluminosilicates and other oxide bases that are formed in a state of foundry together with iron in steelworks, for the formulation of cementitious sludge to be used in drilling oil and gas wells.

The chemical composition of the electric arc furnace slag can have a wide range of variation, as it will depend on several factors. These variations affect the content of the four main components such as the amount of calcium oxide, silica oxide, aluminum oxide and magnesium oxide; as well as other components such as sulfur oxide and iron oxide. In general, the calcium oxide content can be between 38-62%, silica 11-25%, aluminum between 3 and 10% magnesium 4-12%, sulfur 1-2% and iron oxides 3-38% (Cold Rojas and Sánchez de Rojas, 2002). The fact that in this type of steel slag the silicon and calcium oxides are in significantly different proportions does not allow a good thermal stability of the cementitious material above 383 K (Mueller et al., "Portland cement-blast furnace slag blends in oil well cementing applications ". Paper SPE 30513 presented at SPE Annual Technical Conference & Exhibition, Dalias; 1995).

The conversion of the electric arc furnace slag into a latent hydraulic material is achieved when the molten oxide mixture is rapidly cooled to produce a vitreous or amorphous material. Air-cooled slags have virtually no cementing properties.

The vitreous slag of electric arc furnace poor in iron «25%) contains the same components as cement, but in different proportions. This slag is considered a latent hydraulic material, because it requires an activator to show strong cementing properties. This activation can be chemical or thermal. At low temperatures (below 311 K) chemical activation is necessary (Miranda et al., 1997). Chemical activators can be alkalis such as sodium hydroxide, potassium carbonate and calcium carbonate or sulfates.

The electric arc furnace slag to be used in the solidification of the drilling fluid is preferably that referred to in the ASTM C-989 specification

99. Slag that meets this specification is rapidly cooled and is a highly hydraulic material. The vitreous content of this material is greater than 90%. The fineness is between 400 m2 / kg and 700 m2 / kg, although slags with a fineness range of 200 m2 / kg to 1500 m2 / kg have been used. At least 80% of the sample by weight must pass through a 45 micron mesh. The particle distribution size has an average value close to 10 IJm, while the amount of solids less than 2 microns has a limit of 7%. Otherwise, the slag must be subjected to a grinding process in order to reduce the particle size, since this property in the drilling mud is very critical for some properties such as rheology and particle invasion. fines to the hydrocarbon-producing rock formation (Tare et al., "Investigation of blast furnace slag addition to water-based drilling fluids for reduction of drilling fluid invasion into permeable formations". SPE 47800 presented at IADC / SPE Asia Pacific Drilling Conference, Jakarta ; 1998).

The slag of electric arc furnace poor in iron «25%) has densities of lower value than the density of the cement (3.15 g / mi) and blast furnace slags (2.92 g / mi). The average density of electric arc furnace slags is approximately 2.68 g / mi, which can be considered an advantage of these slags with respect to cement and blast furnace slags in obtaining relieved slurries necessary in the cementation of wells with low fracture gradient.

Water-based drilling fluids normally include various additives such as dispersants, dissolved salts, densifiers, formation stabilizers to inhibit harmful interaction between drilling fluid and geological formations, and additives to improve the lubricity of drilling fluid. The water for the water-based drilling fluid may be fresh water, brackish water, brine, seawater or other aqueous fluids.

Many different additives have been used in order to provide the desired properties in each case to water-based drilling fluids. Examples are barium sulfate (barite), bentonite, iron oxide, calcium carbonate, starch, carboxymethylcellulose, acrylonitrile, natural rubber, lignosulfonate, mica, etc. Bentonite is an especially common additive that gives the drilling fluid a thixotropic structure or gel; Lignite is also a common additive that is added to the drilling fluid to control fluid loss; Phosphate and lignosulfonate additives that deflocculate colloidal solids are also common (Economides et al., 1998).

In another aspect of the present invention, the use of a cementitious sludge is claimed, containing between electric arc furnace slag and water-based drilling fluid, whose compressive strength when hardening is low compared to the strengths obtained with the use of blast furnace slag. While with the latter values greater than 1100 psi are obtained at 24 hours at 333 K, with the electric arc furnace slag, 900 psi was not reached under the same conditions. From the point of view of oil and gas well construction, at least 500 psi of compressive strength is required to perform the well integrity test according to ASTM C-989-99.

Likewise, the free fluid is critical for the migration of gas in diverted wells, since experimental tests have shown that free water can favor the creation of channels through which the gas can reach the top of the cemented interval, so it is recommended to design cement slurries with a practically zero free fluid level (Nelson and Guillot, 1990). For the cement sludge made with amorphous slag from an electric arc furnace, the free fluid was almost zero, so it represents an important advantage for a cementing process of hydrocarbon wells.

Another of the main goals that are sought during the cementing process of a hydrocarbon well is zonal isolation. If it is possible to place a cementitious sludge in the annular region capable of withstanding the pressures of the formations without allowing the passage of any fluid, there is an appropriate seal. This migration of fluids can occur through micro-fractures, channels or through the communicated pores of the material that form that seal. The permeability of the cementitious sludge for glass blast furnace and electric arc furnace slags is practically nil, thus ensuring excellent zonal insulation, while the cement can present permeability through its internal structure.

The rheology characterization of a cementitious sludge with electric arc furnace slag is important for evaluating, for example, the pumpability of said mud in the well. In fact, the average low value of the transfer point is notorious.

(0.11 psi at 300 rpm) for the referred cement sludge, so you could run the risk of sedimentation of material when the circulation in the well stops. However, this type of mud has a good stabilization, since the variation in densities from the top to the base does not exceed 0.01 g / ml.

The density values obtained (1.3 g / mi) are low compared to conventional cement slurry (1.8 g / mi), so it would be advantageous to cement wells with a high risk of fracture. It was also observed that a cementitious sludge with electric arc furnace slag did not set for more than six and a half hours. This long time was to be expected because lignosulfonate was used in the mud composition, which is an additive that acts as a retarder during the hydration process of the cement and the electric arc furnace slag.

EXAMPLE OF PREFERRED EMBODIMENT

As an example of a preferred embodiment of the "Procedure for solidification of a water-based drilling fluid in hydrocarbon wells" an electric arc furnace slag is used in remedial cementation operations in the wells of the Amana oil field (Venezuela ), being added to brackish water-based drilling mud (13.5% salt) with lignosulfonate referred to in the table shown below:

Parameter

Value Request

Contained in water

79% (*) -

Serving of bentonite

3.95% -

Lignosulfonate part

0.83% -

Lignite Proportion

0.27% -

PAC-Ul ratio

0.54% -

Barite Percentage

14.1% -

Sand percentage

0.65%

Specific weight

1.2g / ml 1.2-2.15 g / mi

pH

9.8 9.5-11.5

300K plastic viscosity

18cp 5-38 cp

Chloride Concentration

13S00ppm 0-20000ppm

Calcium concentration

160ppm 40-240 ppm

Proportion of solids

22% -

The electric arc furnace slag complied with the requirements of the ASTM C-989-99 specification, presenting properties very similar to those mentioned in this text. Its chemical composition, expressed as oxides of the main elements, was as follows: 41.33% calcium oxide, 22.99% silica, 9.43%, aluminum oxide, 3.20% magnesium oxide, 1.56% of sulfur oxide and 5.21% iron oxides.

Core drilling fluid water with IIgnosulfonate

NaOH or KOH treatment

Adding the electric arc furnace slag required

1 Additive contribution according to each case

Cementing I I 4 -._______.... 1

I Sludge movement to desired location

Solidification in the 310-383K range

As shown in the previous diagram, in a first stage, said drilling mud is mixed with 2 to 40 g of sodium hydroxide or potassium hydroxide per liter of said drilling fluid. Then, the addition of 300 to 900 g of electric arc furnace slag is made for every 5 liters of said drilling fluid containing the corresponding accelerator. Also, after treatment with the electric arc furnace slag, the joint addition of additives required in each particular case occurs. Subsequently, the purpose of the invention is achieved by moving the cementitious sludge to a desired location by a series of techniques.

10 known. Finally, in-situ setting and hardening of the cement sludge occurs, setting times can be controlled from about six hours to more than one day at a temperature in the range of 310 to 383 K.

It is not considered necessary to make this description more extensive so that any person skilled in the art understands the scope of the invention and the advantages derived therefrom. For those skilled in the art, other objects, advantages and characteristics of the invention will be apparent from what is described herein as long as this does not imply an alteration in the essentiality of the invention.

Claims (1)

1.-Procedure for the solidification of a water-based drilling fluid in hydrocarbon wells, characterized by being carried out based on the following sequence: a) Brackish water based drilling fluid (13.5% salt) with lignosulfonate treated with at least one accelerator, preferably sodium hydroxide and / or potassium hydroxide. b) Mix of glass and basic slag of electric arc furnace with the referred drilling fluid treated. c) Displacement of the resulting drilling mud to a pre-selected location 15 in the well. d) In situ hardening and hardening of the cementitious sludge.