MX2008013311A

MX2008013311A - Dispersive riserless drilling fluid.

Info

Publication number: MX2008013311A
Application number: MX2008013311A
Authority: MX
Inventors: Doug Jones; Randy Ray; Jay Forrester
Original assignee: Mi Llc
Priority date: 2006-04-19
Filing date: 2007-04-19
Publication date: 2008-10-27
Also published as: AU2007240399A1; US20070246221A1; BRPI0710460A2; AU2007240399B2; EP2007970A4; EA200870450A1; CA2649574C; CA2649574A1; NO20084782L; MY146020A; EP2007970A2; WO2007124368A3; WO2007124368A2

Abstract

A method for drilling riserless that includes providing a drilling fluid to a drilling assembly for drilling a borehole on a seafloor, the drilling assembly comprising a drill string and a bottomhole assembly, and wherein the drilling fluid includes a brine, and a non-hydratable clay, wherein the drilling fluid is substantially free of hydrating clays, and flowing the drilling fluid and cuttings through an annulus formed by the drill string and the borehole into sea water is disclosed.

Description

PERFORATION FLUID WITHOUT DISPERSING RISE TUBE FIELD OF THE INVENTION The modalities are concerned with drng fluids. More specifically, the embodiments are concerned with drng fluids used in a section without riser tube.

BACKGROUND OF THE INVENTION When wells are drd or terminated in terrestrial formations, various fluids are commonly used in the well for a variety of reasons. Common uses for well fluids include: lubrication and cooling of the cutting surfaces of the drng bit when drng in general or drng (eg drng in an objective oil form), transportation of "cuts" (forming pieces) dislodged by the cutting action of the teeth in a drbit) to the surface, control the formation fluid pressure to prevent bursting, maintain well stability, suspend solids in the well, minimize fluid loss and stabilize the formation through which the well is drd, fracturing the formation in the vicinity of the well, moving the fluid into the well with another fluid, cleaning the well, testing the well, transmitting hydraulic power to the drng bit, the fluid used to emplace a packer, abandon the well or prepare the well for abandonment or otherwise treat the well or formation. During traditional drng practices, mud is pumped to the drstring, through the trephine and upward to the bore of the drng ademe-column to the surface. The viscosity of the mud is designed to transport the drng cuts back to the surface for disposal and density to contain the natural pressure of the well. Drng for oil and gas in very deep water presents problems not found in the exploration of oil and land gas or shallow water. A problem encountered in deep water is the handling of drng fluids. A drng fluid is a fluid specially designed to be circulated through a borehole as the borehole is drd to facilitate the drng operation. The drng fluid circulation path commonly extends from the drng platform through the drng column of the drpipe to the face of the drand back through the annular space between the drng tube column and the drface. borehole to the well head and / or elevator returning to the platform. In addition to the typical functions, the drng fluid also desirably prevents detriment and well digging when drng through water-sensitive formations. Drrs far from the coast have to carry mud to the bottom of the sea, where the hole begins. To do this, they run a steel tube, called an elevator, to extend the hole from the bottom of the sea to the platform. One of the basic and most challenging problems in deepwater operations is the use of the marine lift, which provides a connection between the drship and the wellhead. The lifter serves as a guide for the drpipe to the hole and as a return path of mud to the vessel or ship and also supports control cables and regulation and extermination lines. Deepwater drng operations currently involve the use of a 21-inch external diameter (OD) marine elevator. In drng in shallow water, an elevator system, which is a separate ademe that rises from the seafloor to the base of a drship or drng platform, can be used to return the drng mud to a ship from drng to platform for reuse. The use of an elevator is not without problems and these problems can be exaggerated in deepwater drng projects. One such problem is weight. An elevator of 1, 829 m (6000 ft), 53 cm (21 in) in diameter, maintains drilling mud that has been estimated to weigh approximately 1000 to 1500 tons. It is for this reason that elevatorless drilling methods have been disclosed, particularly for deepwater drilling, in patents such as U.S. Patent No. 6,102,673 issued to Mott, et al. and U.S. Patent No. 4,149,603 issued to Arnold. Additionally, the current drilling technology and nominal pressures required can limit the diameter of the elevator to 48 cm (18 and ¾ of an inch) when drilling in over-pressurized environments. However, because of significant salt thicknesses ranging from 305 cm (1,000 feet) to 3,048 m (10,000 feet) can be found within a few thousand feet of the mud line, larger diameter hole sections are commonly needed at shallow depths to accommodate the multiple arrays or probes required to reach deep reservoir formations. Thus, to drill hole diameters greater than 47.6 cm (18 and ¾ inches) (for example, hole sections 71 cm 61 cm (28 and 24 inches)) or to reduce the costs associated with conventional elevator drilling , the initial shallow portion of the well can be drilled without a riser, with returns (the drilling fluid used and the formation cuts) being discharged to the seabed. There are a number of different types of conventional drilling fluids in which the so-called "drilling mud" compositions are included. Drilling muds comprise high density dispersions of fine solids in an aqueous liquid. Because the sludge used in elevatorless drilling is not commonly circulated to the platform, the cost of "pumping and unloading" must be balanced with the benefits provided by the sludge, when the sludge is pumped to a minimum of 4,542 liters. (1,200 gallons) per minute to a well. For example, when drilling without a riser, seawater alone or combinations of seawater with sludge containing polymers, moisturizing clays and salts to improve inhibition, density, viscosity and other rheological properties have been commonly used. However, while these economically efficient sludges can improve some properties, difficulties have still resulted in drilling still of the accretion and agglomeration, of cutting, accumulation of cuts that cover the well head, formation of ridges in the trepan and hole cleaning issues, such as rubbing, sudden pressure rise and packing, which can lead to pressure issues downhole. These drilling difficulties have been especially problematic when higher density drilling fluids are required. Thus, there is a need for a highly dispersing drilling fluid that will reduce the potential problems with the accretion and agglomeration of cuts, accumulation of cuts, formation of ridges on the trepan and cleaning of the hole.

BRIEF DESCRIPTION OF THE INVENTION In one aspect, the embodiments of the invention with regard to a torqueless piercing method including including providing a drilling fluid to a drill assembly for drilling a hole in a seabed, the drill assembly comprises a drilling column and a set at the bottom of the hole, and wherein the drilling fluid includes a brine and a non-hydratable clay, wherein the drilling fluid is substantially free of moisturizing clays and flowing drilling fluid and cuts to through an anulus formed by the sounding column and the borehole to the sea water. In another aspect, the embodiments of the invention are concerned with a method for drilling without a riser which includes providing a drilling fluid to a drilling assembly for drilling a borehole in a seabed, the drilling assembly comprising a drilling column and a drilling rig. the bottom of the hole, and wherein the drilling fluid includes a brine, an attapulgite clay and an alkali metal or alkaline earth metal salt wherein the drilling fluid is substantially free of hydrating clays and flowing the drilling fluid and cuts through an anulus formed by the drilling column and the borehole to the seawater. In still another aspect, the embodiments of the invention are concerned with a borehole fluid that includes an aqueous fluid, attapulgite clay and a salt of an alkali metal or alkaline earth metal, wherein the borehole fluid is substantially free of hydrating clays. Other aspects and advantages of the invention will become apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a schematic view of an open hole drilling according to a modality disclosed herein.

DETAILED DESCRIPTION In one aspect, the embodiments disclosed herein are concerned with dispersing drilling fluids and methods of drilling with these fluids. In particular, the embodiments disclosed herein are concerned with drilling fluids used in drilling a section of a borehole without an elevator. In one embodiment, a drilling fluid may include a brine and a non-hydratable clay. As used herein, "brine" is defined to include any aqueous saline solution and "non-hydratable clay" is defined as those clays that do not swell appreciably in either fresh or salt water.

Brine In various embodiments of the drilling fluid disclosed herein, the brine may include seawater, aqueous solutions wherein the salt concentration is lower than that of seawater or aqueous solutions where the salt concentration is greater than that of sea water. The salinity of seawater can range from about 1 percent to about 4.2 percent salt by weight based on the total volume of seawater. Salts that can be found in seawater include, but are not limited to, sodium, calcium, sulfur, aluminum, magnesium, potassium, strontium, silicon, lithium and phosphorus of chlorides, bromides, carbonates, iodides, chlorates, bromates, formates, nitrates, oxides and fluorides. Salts that can be incorporated in a given brine include any of one or more of those present in natural seawater or any dissolved organic or inorganic salts. Additionally, the brines that can be used in the drilling fluids disclosed herein can be natural or synthetic, the synthetic brines tend to be much simpler in constitution. In one embodiment, the density of the drilling fluid can be controlled by increasing the salt concentration in the brine (up to saturation). In a particular embodiment, a brine may include halide or carboxylate salts of mono- or divalent metal cations such as cesium, potassium, calcium, zinc and / or sodium.

Clays The drilling fluids disclosed herein may also contain a non-hydratable clay. In some embodiments, the non-hydratable clay may be a clay having a needle-like structure or chain-like structure. In several other fashions, the non-hydratable clay can be selected from at least one of attapulgite or sepiolite clays. In a particular embodiment, the non-hydratable clay includes attapulgite clay. So long as the non-hydratable clays do not swell substantially in either fresh water or salt water, they can still operate to thicken the salt solutions. This thickening can be attributed to what is believed to be a unique orientation of colloidal clay particles loaded into the dispersion medium and not actual "hydration". Since the term "non-hydratable" refers to the characteristic lack of the swelling clay, ie, measurable volume increase, in the presence of salt water, a given clay swelling in seawater can be tested by a described procedure in an article by K. Norrish, published as "The swelling of ontmorillonite", Disc. Faraday Soc. vol. 18, 1954 pp. 120-134. This test involves immersing the clay for about 2 hours in a solution of deionized water and about 4 weight percent of sodium chloride per volume of salt solution. Similarly, a swelling of given clay in fresh water can be tested by an analogous procedure in which sodium chloride is excluded. A "non-hydratable" clay is defined in a form as one that, under this test, swells less than 8 times in volume compared to its dry volume. In another embodiment, a non-hydratable clay exhibits swelling of the order of less than 2 times, less than 0.3 times, in another mode and less than 0.2 times in yet another mode. In further embodiments, the drilling fluids disclosed herein may be substantially free of hydrating clays. As used herein, "hydrating clays" is defined as those clays that swell appreciably (i.e., increase their volume by an amount of at least 8 times) either in fresh or salt water and "substantially free" it is defined as an amount that does not significantly affect dispersibility. The moisturizing clays may include those clays that swell appreciably in contact with fresh water, but not when contacted with salt water, which include, for example, clays containing sodium montmorillonite, such as bentonite. Many moisturizing clays have a leaf-like structure or plate-like structure.

Salts In various embodiments, the perforation fluid disclosed herein may also contain at least one additional salt, which includes any salt that may be incorporated in brines, as disclosed herein. In particular embodiments, at least one of sodium chloride, calcium chloride, potassium chloride and sodium carbonate can be incorporated into the drilling fluids disclosed herein. In one embodiment, the at least one additional salt can be incorporated into the drilling fluid disclosed herein in an amount ranging from about 0.5 weight percent to salt saturation.

Additives The drilling fluids disclosed herein may optionally contain various additives, depending on the end use of the fluid. For example, weighting agents, deflocculants and combinations thereof may be added in the fluid compositions disclosed herein for additional functional properties. The addition of such agents should be well known to those skilled in the art to formulate fluids and drilling muds. However, it should be noted that the addition of such agents should not adversely interfere with the properties associated with the ability of the sludge to disperse ++++ cuts as disclosed herein. Suitable weighting agents or density materials for use in the fluids disclosed herein include for example galena, hematite, magnetite, iron oxides, ilmenite, barite, siderite, celestite, dolomite, calcite and the like. The amount of such aggregate material, if any, depends on the desired density of the final composition. Commonly, the weight material is aggregated to result in a drilling fluid density of up to approximately 2.3 kg / liter (19 pounds per gallon) in an embodiment; and that fluctuates from 1.1 Kg / liter to 1.7 Kg / liter (9.5 to 14 pounds per gallon) in another modality. De-flocculants or slimming agents that can be used in the drilling fluids disclosed herein include for example lignosulfonates, modified lignosulfonates, phosphonate, tannins and low molecular weight water soluble polymers such as polyacrylates. Deflocculants are commonly added to a drilling fluid to reduce flow resistance and control gelation tendencies. In a particular embodiment, a deflocculant may be desirable when a drilling fluid is formed from heavier mud diluted with seawater. TA NATHIN, an oxidized Ignite, is an example of a deflocculant that is available from -I L.L.C. (Houston Texas) .

Formulations In one embodiment, the drilling fluid can be formulated to have a density range of about 1 kg / liter to 1.7 kg / liter (9 to 14 pounds per gallon). The drilling fluid can be formulated initially to have the desired formulation. Alternatively, the drilling fluid can be formed from a concentrated slurry, such as a slurry of 16 pounds per gallon or heavier, which will be combined with a brine before use to the desired formulation. Those who have ordinary skill in the art will appreciate that other densities can be used as desired. When combined from a slurry and a brine, the sludge may optionally contain a salt, such as an alkali metal or alkaline earth metal salt. In one embodiment, the piercing fluid point has a pH greater than about 6. In another embodiment, the piercing fluid may have a pH ranging from about 7.5 to 12. The pH of the piercing fluid can be made with the addition of Acid or basic additives, as recognized by the one experienced in the art. For example, caustic soda and citric acid can be used to increase or decrease the pH of a fluid, respectively.

Drilling Method When drilling from a boat or floating platform, the upper portion of the well is frequently drilled by open hole drilling in which no conduit is provided for the return of drilling / cutting fluid to flow to the platform. As shown in Figure 1, to pierce the initial upper portion of the well 10, a drill column 14 commonly extends unsupportedly from a ship or platform 12 through the water to the seabed 16 without an elevator. In more detail, first an external ademe 18, known as "structural ademe", which commonly has a diameter of 76 cm (30 inches) or 91 cm (36 inches), is installed in the uppermost section of the well, with an accommodation low pressure well head (not shown separately) connected to it. In soft formations, the structural ademe 18 can be applied to the jet in its place. In this process, a drill assembly including a drill string 14 and a bottom hole assembly (BHA) (not shown separately) and ademe 20 is lowered to the seabed goes to the drill string 14. The BHA includes a drilling bit 16 and may also include other components such as drill collars and a downhole motor (not shown separately). The trepan 16 is positioned just below the lower end of the structural ademe 20 and is sized to drill a bore 22 with a diameter slightly smaller than the diameter of the ademe 20. As the bore 22 is drilled, the structural ademe 20 moves down with the BHA. The weight of the structural ademe 20 and the BHA drives the ademe 20 to the sediments. The structural ademe 20, in its final position, can be extended down to a depth of 46 m (150 ft.) To 122 m (400 ft.), Depending on the conditions of the formation and the final well design. After the structural ademe 20 is in place, it can be released from the drill string or drill string 14 and the BHA. The drilling column or drilling column 14 and the BHA can be returned to the platform or alternatively, they can be lowered further to drill below the structural ademe. Alternatively, the structural ademe 20 can be installed in a two-stage process. First, a larger bore than the structural ademe is drilled. Then, the structural ademe 20 is run to the bore 22 and is cemented in place. Commonly, the low pressure well head housing (not shown separately) is connected to the upper end of the structural ademe 20 and installed at the same time, such that the structural ademe 20 extends below the sea floor with the head housing of low pressure well above the seabed. Once the structural ademe 20 and the low pressure well head housing are installed, the drill bit 16 in the drill string 14 drills down under the structural ademe 20 to drill a new hole section using open hole drilling for an intermediate ademe 24, known as "lead ademe", which may be for example 20 inches in diameter. Thus, the structural ademe 20 guides the BHA as it begins to drill the conductive lead interval 24. After the hole section for the conductive lead 24 is drilled, the BHA is returned to the surface. Then the conductor die 24, with a high-pressure well head housing connected to its upper end and an exposed float valve at its lower end (not shown separately) is run to the perforated conductor hole section extending below the structural ademe 20. The conductive ademe 24 is cemented in its place in a well-known manner, with the float valve which prevents the cement from flowing upwards to the conductor ademe after the placement of the cement. The conductive ademe 24 can generally extend down to a depth of 305 m to 914 m (1,000 to 3,000 ft) below the seabed, depending on the conditions of the formation and the final well design. The high pressure well head housing (not shown separately) can be coupled with the low pressure wellhead housing (not shown separately) to form the seabed well head, thereby consuming the non-elevating portion of the well. drilling operations. The installation of a submarine burst prevention (BOP) stack can be transported to the sea floor by an elevator and be retained on the underwater wellhead housing for subsequent elevator drilling. During the opening hole drilling shown in Figure 1, the drilling fluid flows from the drilling column or drilling column 14 and outwardly from the drilling bit 16 as shown by the downward arrows 26. The fluid flow from perforation continues through the annulus between the bore 22 and the drilling assembly 14, 16. As the drilling fluid flows through this bore, it can transport drilled cuts through the borehole, indicated by the dates upwards 28 and it can leave the well to be dispersed to the sea, as indicated by the arrows 30. Therefore, in the open-hole drilling, the returns, that is, the drilling fluid, cuts and well fluid, are discharged on the floor marine and are not transported to the surface.

EXAMPLE The following examples were used to test the effectiveness of the drilling fluids disclosed herein in the dispersion of cuts. The drilling muds were formulated having the following components, all of which are commercially available, as shown below in Table 1. MI GEL® is an example of bentonite clay, SALT GElf is an example of attapulgite clay, TANNATHIN * is a lignite and DUOVIS "is a xanthan gum, all of which are commercially available from MI LLC (Houston, Texas).

Table 1: 16 ppg mud formulations The various slurry formulations were then combined with seawater and their rheological properties were determined using a Fann Model 35 viscometer, available from Fann Instrument Company. Then the sludge was subjected to dispersion tests, where 20 grams of shale, dried for 16 hours at 93 ° C (200 ° F) and sized to mesh -6 / + 20, was added to the mud and laminate combinations in warm for 16 hours at 65.5 ° C (150 ° F). Seawater was used as a target. After hot rolling, the samples were cooled. An 80 mesh screen was used to recover an undispersed shale. The percent recovery can be determined by comparing the amount of shale recovered with the initial 20 grams of shale used. A lower percent recovery indicates greater dispersion of the shale by the fluid. The results are shown in Tables 2a and 2b.

Table 2a: Dispersion Test Table 2b: Dispersion test From the results shown in Table 2a and 2b, a comparison of samples 9-11 (Lode E) with Samples 2-5 (Lode A) shows increased dispersion of the shale to the drilling fluid containing attapulgite clay with with respect to that which contains bentonite clay. Similarly, a comparison of Samples 7 (sludge C) with Sample 8 (Sludge D) shows increased scattering of the shale to the drilling fluid containing attapulgite with respect to that containing polymer. Additionally, the dispersion can be further increased to higher pHs, as shown by comparing Samples 12-16 (FJ sludges) to each other and after addition of a salt, as shown by comparing Samples 6 (Sludge B) with Sample 7 (Sludge C). Advantageously, the embodiments disclosed herein may provide a drilling fluid that can be used in open hole drilling. The fluids disclosed herein can provide the rheological properties needed to drill without an elevator. Additionally, by increasing the amount of dispersion of cuts to fluids and subsequently seawater, fluids can at least reduce the accretion and agglomeration of cuts, accumulation of cuts that cover the wellhead, formation of ridges on the trephine and hole cleaning issues, such as rubbing, sudden pressure increase and packing, which can lead to pressure issues. While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate that other embodiments may be devised that do not deviate from the scope of the invention as disclosed in the present. Thus, the scope of the invention should be limited only by the appended claims.

Claims

CLAIMS 1. A method for elevatorless drilling, characterized in that it comprises: providing a drilling fluid to a drilling assembly for drilling a borehole on a seabed, the drill assembly comprising a drilling column or drilling column and an assembly in the bottom of the hole, and wherein the drilling fluid comprises: a brine; and a non-hydratable clay, wherein the drilling fluid is substantially free of moisturizing clays; and flowing the drilling fluid and cuts through an anulus formed by the drilling column or drilling column and the borehole to the seawater.
2. The method according to claim 1, characterized in that it further comprises: inserting a hole into the hole.
3. The method according to claim 2, characterized in that the ademe is inserted into the hole as the hole is drilled.
4. The method according to claim 2, characterized in that the ademe is inserted into the hole after the hole is drilled.
5. The method according to claim 1, characterized in that the non-hydratable clay comprises at least one of attapulgite and sepiolite clays.
6. The method according to claim 1, characterized in that the drilling fluid fluctuates from about 9.0 to 14 ppg.
The method according to claim 1, characterized in that the drilling fluid has a pH ranging from about 7.5 to 12.
The method according to claim 1, characterized in that the drilling fluid comprises at least one of a weighting agent, a deflocculant, a fluid loss control agent and combinations thereof.
The method according to claim 1, characterized in that the drilling fluid further comprises a salt of an alkali metal or alkaline earth metal.
A method for drilling a formation, characterized in that it comprises: providing a drilling fluid to a drilling assembly for drilling a borehole on a seabed, the drilling assembly comprising a drilling column and a set at the bottom of the bore, and wherein the drilling fluid comprises: a brine; an attapulgite clay; and a salt of an alkali metal or alkaline earth metal, wherein the slurry is substantially free of hydrating clays; and flowing the drilling and cutting fluid through an anulus formed by the borehole and the borehole to the seawater.
The method according to claim 10, characterized in that the drilling fluid fluctuates from about 9.0 to 14 ppg.
12. The method in accordance with the claim 10, characterized in that the drilling fluid has a pH ranging from about 7 to 12. The method according to claim 10, characterized in that the drilling fluid further comprises at least one of a weighting agent, a deflocculant. , a fluid loss control agent and combinations thereof. 14. A drilling fluid characterized in that it comprises: an aqueous fluid; an attapulgite clay; and a salt of an alkali metal or alkaline earth metal, wherein the drilling fluid is substantially free of hydrating clays. 15. The drilling fluid according to claim 14, characterized in that the non-hydratable clay comprises at least one of attapulgite and sepiolite clays. 16. The drilling fluid according to claim 14, characterized in that the drilling fluid fluctuates from about 9.0 to 14 ppg. 17. The drilling fluid according to claim 14, characterized in that the drilling fluid has a pH ranging from about 7 to 12. The drilling fluid according to claim 14, characterized in that it also comprises: minus one of a wetting agent, a deflocculant and combinations thereof.