Ultrahigh-density water-based drilling fluid

Abstract

The invention relates to an ultrahigh-density water-based drilling fluid, and belongs to the field of petroleum drilling. The drilling fluid is composed of a base fluid and a weighting agent, and the density of the drilling fluid is 2.30 g / cm < 3 > or above; the base solution is prepared from the following components in percentage by mass: 1.0 to 1.2 percent of bentonite, 0.1 to 0.2 percent of caustic soda, 8 to 10 percent of KCl, 0.5 to 0.8 percent of polyaluminum chloride, 0.5 to 0.7 percent of inhibitor, 8 to 13 percent of filtrate reducer, 3.5 to 5.0 percent of lubricant, 5 to 8 percent of superfine calcium carbonate and 2 to 3 percent of white asphalt; wherein the mass fraction is the ratio of the mass of each component to the mass of water; the weighting agent is iron ore powder, barite and ultra-fine barite; the mass ratio of the iron ore powder to the barite to the ultra-fine barite is (4-6): (2-3): (2-3). The ultrahigh-density water-based drilling fluid disclosed by the invention has good rheological property, inhibition property, high-temperature and high-pressure aging resistance, filtrate loss reduction property, sedimentation stability, pressure-bearing plugging capacity and pollution resistance.

Description

Technical Field

[0001] The present invention relates to an ultra-high density water-based drilling fluid, belonging to the field of oil drilling. Background Art

[0002] In oil drilling, drilling fluid is a key technology for safe drilling and well completion. For conventional normal formation pressure coefficients of 1.0 - 1.07, the commonly used water-based drilling fluid systems in drilling can basically meet the construction requirements. However, for shallow formations with strong mud-making and abnormally high-pressure formations caused by water injection and polymer flooding, it is necessary to increase the density of the drilling fluid to balance the wellbore pressure to ensure well control safety. As the density of the drilling fluid increases, the solid content in the system increases, and the higher the drilling fluid density, the more difficult it is to control the rheological properties. Therefore, in drilling in abnormally high-pressure formations with water injection and polymer flooding, whether it is possible to ensure well control safety, prevent complications, and ensure well completion, the stability of the performance of the shallow high-density mud-making drilling fluid system is crucial.

[0003] The density of the high-density drilling fluid is between 1.8 - 2.3 g / cm 3 while the density of the ultra-high density drilling fluid system reaches 2.3 g / cm 3 or more. Compared with the high-density drilling fluid, the ultra-high density drilling fluid requires stronger suspension ability, inhibition, better lubrication performance, and flow performance that meet the construction requirements. However, due to the excessively high content of solid weighting agents in the ultra-high density drilling fluid, the non-structural viscosity formed by the solid weighting agents will exceed the structural viscosity formed by the hydration of clay mineral particles, etc., and even directly control the rheological parameters of the ultra-high density water-based drilling fluid. And during the drilling process, affected by environmental factors and additives, the ultra-high density drilling fluid is extremely prone to being contaminated, which has an adverse impact on downhole safety. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-high density water-based drilling fluid to solve the problems of poor rheological properties and easy contamination of the water-based drilling fluid when its density is ultra-high in the prior art.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] An ultra-high density water-based drilling fluid, composed of a base fluid and a weighting agent, with a density of 2.30 g / cm 3 or more; the base fluid includes the following components by mass fraction: 1.0 - 1.2% bentonite, 0.1 - 0.2% caustic soda, 8 - 10% KCl, 0.5 - 0.8% polyaluminum chloride, 0.5 - 0.7% inhibitor, 8 - 13% filtration reducer, 3.5 - 5.0% lubricant, 5 - 8% ultra-fine calcium carbonate, 2 - 3% white asphalt; where the mass fraction is the mass ratio of each component to the mass of water;

[0007] The weighting agent is iron ore powder, barite and ultra-fine barite; the mass ratio of the iron ore powder, barite and ultra-fine barite is (4-6):(2-3):(2-3).

[0008] The ultra-high density water-based drilling fluid of the present invention has good rheology, inhibition, high temperature and high pressure anti-aging property, filtration reduction property, settlement stability, pressure-bearing plugging ability and anti-pollution property, and the raw materials of the drilling fluid of the present invention are easily available and the production cost is relatively low, and it has broad application prospects in low-temperature and strong mud-making injection wells.

[0009] In order to ensure good non-structural viscosity at ultra-high density of the formulation system, preferably, the median particle size D 50 of the iron ore powder is 25-27 μm, the median particle size D 50 of the barite is 10-13 μm, and the median particle size D 50 of the ultra-fine barite is 1-2 μm.

[0010] Preferably, the median particle size D 50 of the ultra-fine calcium carbonate is 3-5 μm.

[0011] In order to improve the filtration reduction property, preferably, the filtration reducer is composed of sulfonated phenolic resin, lignite resin and high temperature and high salt resistant filtration reducer.

[0012] Preferably, the mass ratio of the sulfonated phenolic resin, lignite resin and high temperature and high salt resistant filtration reducer is (3-5):(3-5):(2-3). The combination of these three filtration reducers has higher filtration reduction property and further improved high temperature and high salt resistance.

[0013] In order to improve the lubricity and fluidity of the drilling fluid, preferably, the lubricant is one or two of fatty acid ester lubricants and emulsified paraffin wax.

[0014] Preferably, the lubricant is fatty acid ester lubricant and emulsified paraffin wax, and the mass ratio of the fatty acid ester lubricant and emulsified paraffin wax is (2-3):(1.5-2). The fatty acid ester lubricant is further preferably SMLUB-E2.

[0015] Preferably, the bentonite is sodium bentonite. Brief Description of the Drawings

[0016] Figure 1 It is a diagram showing the relationship between the injection volume and the pressure-bearing plugging ability in Experimental Example 7 of the present invention. Detailed Embodiments

[0017] The technical solutions of the present invention will be further described below in conjunction with the detailed embodiments.

[0018] I. The specific embodiments of the ultra-high density water-based drilling fluid of the present invention are as follows:

[0019] Example 1

[0020] The ultra-high density water-based drilling fluid of this example is composed of a base fluid and weighting agents. The base fluid is composed of the following components by mass fraction: 1.2% sodium bentonite, 0.2% caustic soda, 8% KCl, 0.5% polyaluminum chloride, 0.5% amino silanol HAS, 3% sulfonated phenolic resin SMP-2, 3% lignite resin SPNH, 2% high-temperature and high-salt filtration loss reducer SPC, 2% high-density lubricant SMLUB-E2, 1.5% emulsified paraffin SL-1, 8% ultra-fine calcium carbonate QS-2, 2% white asphalt DWF-1, and the solvent is water. In practical applications, iron ore powder, barite and ultra-fine barite weighting agents are added to adjust the density of the base fluid to 2.30 - 2.50 g / cm 3 , where the mass ratio of iron ore powder, barite to ultra-fine barite is 5:2.5:2.5.

[0021] Example 2

[0022] The ultra-high density water-based drilling fluid of this example is composed of a base fluid and weighting agents. The base fluid is composed of the following components by mass fraction: 1.0% sodium bentonite, 0.15% caustic soda, 10% KCl, 0.8% polyaluminum chloride, 0.6% amino silanol HAS, 4% sulfonated phenolic resin SMP-2, 4% lignite resin SPNH, 2.5% high-temperature and high-salt filtration loss reducer SPC, 2.5% high-density lubricant SMLUB-E2, 2% emulsified paraffin SL-1, 5% ultra-fine calcium carbonate QS-2, 2.5% white asphalt DWF-1, and the solvent is water. In practical applications, iron ore powder, barite and ultra-fine barite weighting agents are added to adjust the density of the base fluid to 2.30 - 2.50 g / cm 3 , where the mass ratio of iron ore powder, barite to ultra-fine barite is 5:2.5:2.5.

[0023] Example 3

[0024] The ultra-high density water-based drilling fluid of this example is composed of a base fluid and weighting agents. The base fluid is composed of the following components by mass fraction: 1.1% sodium bentonite, 0.2% caustic soda, 10% KCl, 0.75% polyaluminum chloride, 0.7% amino silanol HAS, 5% sulfonated phenolic resin SMP-2, 5% lignite resin SPNH, 3% high-temperature and high-salt filtration loss reducer SPC, 3% high-density lubricant SMLUB-E2, 2% emulsified paraffin SL-1, 6% ultra-fine calcium carbonate QS-2, 2% white asphalt DWF-1, and the solvent is water. In practical applications, iron ore powder, barite and ultra-fine barite weighting agents are added to adjust the density of the base fluid to 2.30 - 2.50 g / cm 3 , where the mass ratio of iron ore powder, barite to ultra-fine barite is 5:2.5:2.5.

[0025] II. Examples of the preparation method of the ultra-high density water-based drilling fluid of the present invention

[0026] Example 4

[0027] This example is the preparation method of the ultra-high density water-based drilling fluid in Example 3, and the following steps are adopted:

[0028] Add 3.85 g of sodium bentonite to 350 ml of water, stir at high speed for 20 min, put it into a sealed container and hydrate at room temperature for 24 h to obtain 1.1% sodium bentonite slurry; add 17.5 g of sulfonated phenolic resin SMP-2 to the above sodium bentonite slurry under high-speed stirring and stir at high speed for 20 min, add 17.5 g of lignite resin, 10.5 g of high-temperature and high-salt filtration reducer SPC, 0.7 g of caustic soda and 21 g of ultrafine calcium carbonate QS-2, stir at high speed for 15 min, then add 35 g of KCl, 2.63 g of polyaluminum chloride, 2.45 g of amino silanol HAS, stir at high speed for 15 min, add 10.5 ml of high-density lubricant SMLUB-E2, 7 ml of emulsified paraffin, 7 g of white asphalt, stir at high speed for 15 min, and finally add 410 g of iron ore powder, 205 g of barite, 205 g of superfine barite powder, stir at high speed for 15 min, and a ultra-high density drilling fluid with a density of 2.30 g / cm 3 can be obtained.

[0029] Example 5

[0030] The preparation method of the ultra-high density water-based drilling fluid in this example is basically the same as that in Example 4, except that: finally add 465 g of iron ore powder, 233 g of barite, 233 g of superfine barite powder, stir at high speed for 15 min, and a ultra-high density drilling fluid with a density of 2.40 g / cm 3 can be obtained.

[0031] Example 6

[0032] The preparation method of the ultra-high density water-based drilling fluid in this example is basically the same as that in Example 4, except that: finally add 500 g of iron ore powder, 250 g of barite, 250 g of superfine barite powder, stir at high speed for 15 min, and a ultra-high density drilling fluid with a density of 2.50 g / cm 3 can be obtained.

[0033] III. Comparative examples

[0034] Comparative example 1

[0035] The ultra-high density water-based drilling fluid of this comparative example consists of a base fluid and weighting agents. The base fluid is composed of the following components by mass fraction: 2% sodium bentonite, 0.2% caustic soda, 10% KCl, 0.75% polyaluminum chloride, 0.7% amino-silanol HAS, 5% sulfonated phenolic resin SMP-2, 5% lignite resin SPNH, 3% high-temperature and high-salt filtration reducer SPC, 3% high-density lubricant SMLUB-E2, 6% ultra-fine calcium carbonate QS-2, 2% emulsified paraffin SL-1, 2% white asphalt DWF-1, and the solvent is water. In actual application, iron ore powder, barite, and ultra-fine barite weighting agents are added to adjust the density of the base fluid to 2.30 - 2.50 g / cm 3 , where the mass ratio of iron ore powder, barite, and ultra-fine barite is 5:2.5:2.5.

[0036] Comparative Example 2

[0037] The ultra-high density water-based drilling fluid of this comparative example is basically the same as that of Example 3, except that: the weighting agents are barite and ultra-fine barite, and the mass ratio of barite to ultra-fine barite is 5:5.

[0038] IV. Experimental Examples

[0039] The measurement methods for the performance indicators involved in the following experimental examples are as follows:

[0040] PV: That is, plastic viscosity, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO 10414-1:2008;

[0041] AV: That is, apparent viscosity, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO 10414-1:2008;

[0042] YP: That is, yield point, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO 10414-1:2008;

[0043] FL API : That is, water loss at normal temperature and pressure, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO10414-1:2008;

[0044] FL HTHP : That is, high-temperature water loss, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO 10414-1:2008;

[0045] K f : Mud cake friction coefficient, and the measurement method refers to the national standard GB / T 16783.1 - 2014 / ISO 10414-1:2008.

[0046] Experimental Example 1

[0047] In this experimental example, the basic properties of the ultra-high density water-based drilling fluid in Example 1 were evaluated, and the results are shown in Table 1.

[0048] Table 1 Evaluation of the Basic Properties of Ultra-High Density Water-Based Drilling Fluid

[0049]

[0050] Experimental Example 2

[0051] In this experimental example, the high-temperature aging performance of the ultra-high density water-based drilling fluids with different densities in Comparative Example 1, Comparative Example 2, Example 4, Example 5, and Example 6 was evaluated, and the results are shown in Table 2.

[0052] Specifically, it was heat-rolled at 120 °C for 16 h, and its rheology, high-temperature and high-pressure water loss, sodium bentonite content, and friction coefficient were measured.

[0053] Table 2 Evaluation of the High-Temperature Aging Performance of Drilling Fluids with Different Densities

[0054]

[0055] As can be seen from Table 2, the rheology of the drilling fluid in the comparative example is poor, the funnel viscosity FV and the yield point YP values are on the high side, which is not conducive to the on-site maintenance and treatment of the drilling fluid, and the weighting agent ratio in Comparative Example 2 is unreasonable, resulting in too high viscosity and shear force; while the drilling fluid in the examples of the present invention has an apparent viscosity of less than 110 mPa·s at high density, a high-temperature and high-pressure water loss of less than 14 ml, and a friction coefficient of less than 0.23, indicating that the water-based drilling fluid of the present invention has a density of 2.3 - 2.5 g / cm 3 When it is, it has good rheological properties, low water loss, and low mud cake friction coefficient.

[0056] Experimental Example 3

[0057] In this experimental example, different proportions (1% - 3%) of sodium bentonite were mixed into the ultra-high density (2.50 g / cm 3 ) water-based drilling fluid in Example 6. After stirring at high speed (10,000 rpm / min) for 30 min, its rheology and aging water loss performance were measured. Referring to the national standards GB / T 16783.1 - 2014 / ISO 10414 - 1:2008 and GB / T 29170 - 2012, the heat-rolling aging conditions were: 120 °C / 16 h, and the results are shown in Table 3.

[0058] Table 3 Influence of Different Sodium Bentonite Dosages on the Performance of High-Density Drilling Fluid

[0059]

[0060] In Table 3, φ600, φ300, φ6, and φ3 represent the readings of the outer cylinder of the six-speed rotational viscometer at rotations such as 600 r / min and 300 r / min; FL API FL in / hk API is the medium-pressure filtration loss, and hk is the thickness of the mud cake on the filter paper after medium-pressure filtration loss.

[0061] As can be seen from Table 3, when 1% bentonite is added to the ultra-high-density water-based drilling fluid, its rheology is better and the filtration loss at high temperature and high pressure is lower, indicating that the ultra-high-density water-based drilling fluid of the present invention can effectively resist 2% bentonite pollution, and the change in the performance of the drilling fluid is acceptable.

[0062] Experimental Example 4

[0063] In this experimental example, different proportions (1% - 3%) of cuttings powder were mixed into the ultra-high-density (2.50 g / cm 3 ) water-based drilling fluid in Example 6, stirred at a high speed (10,000 rpm / min) for 30 min, and then its rheology and aging filtration loss performance were measured. The cuttings of the Weigang Oilfield shale were dried and crushed indoors, passed through a 100-mesh sieve, and then the undersize was added to each water-based drilling fluid respectively. Then, the water-based drilling fluid containing cuttings was heat-rolled at 120 °C for 16 h. Finally, the rheological properties and API of the mixed liquid after heat-rolling were tested FL . Its rheology and aging filtration loss performance were measured. The measurement method refers to the national standards GB / T 16783.1 - 2014 / ISO10414 - 1:2008 and GB / T 29170 - 2012. Among them, the aging conditions were: 120 °C / 16 h. The results are shown in Table 4.

[0064] Table 4 Influence of different cuttings powder addition amounts on the performance of high-density drilling fluid

[0065]

[0066] As can be seen from Table 4, when 2% cuttings powder is added to the ultra-high-density water-based drilling fluid, its rheology is better and the filtration loss is lower, indicating that the ultra-high-density water-based drilling fluid of the present invention can effectively resist 2% cuttings powder pollution.

[0067] Experimental Example 5

[0068] In this experimental example, the suspension stability performance of ultra-high-density water-based drilling fluids at different densities was measured.

[0069] In this experimental example, ultra-high-density water-based drilling fluids with different densities of Comparative Example 1, Comparative Example 2, Example 4, Example 5, and Example 6 were respectively prepared. Through indoor experiments, the density after just being prepared and stirred, the upper-layer density and the lower-layer density after sedimentation at 120 °C for 48 hours were measured. The results are shown in Table 5.

[0070] Table 5 Suspension Stability of Different High-Density Drilling Fluids for 48 Hours

[0071] Experiment Number ρ upper / g / cm3 ρ lower / g / cm3 Δρ / g / cm3 Comparative Example 1 2.50 2.50 0 Comparative Example 2 2.51 2.51 0 Example 4 2.32 2.32 0 Example 5 2.41 2.42 0.02 Example 6 2.49 2.51 0.02

[0072] As can be seen from Table 5, the drilling fluids of the comparative examples and the examples all showed good suspension stability. The ultra-high-density water-based drilling fluid of the present invention has good sedimentation stability, and the density difference between the upper and lower layers and the initial density of the base slurry is less than 0.02 g / cm 3 .

[0073] Experimental Example 6

[0074] This experimental example measures the strong inhibition performance of the ultra-high-density water-based drilling fluids of Example 6, Comparative Example 1, and Comparative Example 2.

[0075] This experimental example selects the cuttings returned from 1495 m of Well Wei 535 to test the shale rolling recovery rate of the ultra-high-density (2.50 g / cm 3 ) water-based drilling fluid. The test operation steps refer to SY / T 5613-2016. Among them, the measurement conditions are 120 °C / 16 h, and the results are shown in Table 6.

[0076] Table 6 Cuttings Recovery Rate Test

[0077]

[0078] As can be seen from Table 6, the primary recovery rate of the ultra-high-density water-based drilling fluid of Example 6 of the present invention for the cuttings is 94.56%, and the secondary recovery rate is 95.35%. Compared with the cuttings recovery rates of the comparative examples and fresh water, the inhibition is strong.

[0079] Experimental Example 7

[0080] This experimental example measures the pressure-bearing plugging ability of the ultra-high-density water-based drilling fluid of Example 6.

[0081] The test standard refers to GB / T 29170-2012. This experimental example uses a high-temperature and high-pressure sand bed filter loss instrument to test the invasion amount of the 40-60 mesh sand bed at 120 °C. The results are shown in Table 7 and Figure 1 .

[0082] Table 7 Pressure-Bearing Plugging Performance of Sand Bed

[0083] Extrusion Volume / mL Extrusion Pressure Mpa / 30 min 3.6 3.5 7.7 7.5 12 9.8 15 10.4 21 14.8

[0084] As can be seen from Table 7, when the injection volume in the 40-60 mesh sand bed is 21 mL, the pressure-bearing reaches 14.8 MPa, the pressure-bearing plugging ability is strong, and a plugging layer is quickly formed to achieve the purpose of rapid plugging.

Claims

1. An ultra-high density water-based drilling fluid, characterized in that: It is composed of base liquid and weighting agent, with a density of 2.30g / cm 3 The base liquid comprises the following components by mass fraction: 1.0-1.2% bentonite, 0.1-0.2% caustic soda, 8-10% KCl, 0.5-0.8% polyaluminium chloride, 0.5-0.7% inhibitor, 8-13% fluid loss reducer, 3.5-5.0% lubricant, 5-8% ultrafine calcium carbonate, 2-3% white asphalt; wherein the mass fraction is the ratio of the mass of each component to the mass of water; The weighting agent is iron ore powder, barite and ultrafine barite; the mass ratio of the iron ore powder, barite and ultrafine barite is (4-6):(2-3):(2-3).

2. The ultra-high density water-based drilling fluid according to claim 1, characterized in that: The median particle size of the iron ore powder is D 50 The median particle size of the barite is 25-27 μm. 50 The median particle size of the ultrafine barite is 10-13 μm. 50 1-2μm.

3. The ultra-high density water-based drilling fluid according to claim 1, characterized in that: The median particle size of the ultrafine calcium carbonate is D 50 3-5μm.

4. The ultra-high density water-based drilling fluid according to claim 1, characterized in that: The fluid loss reducer consists of sulfonated phenolic resin, lignite resin and temperature and salt resistant fluid loss reducer.

5. The ultra-high density water-based drilling fluid according to claim 4, characterized in that: The mass ratio of the sulfonated phenolic resin, the lignite resin and the temperature-resistant and salt-resistant fluid loss reducer is (3-5): (3-5): (2-3).

6. The ultra-high density water-based drilling fluid according to claim 1, characterized in that: The lubricant is one or both of fatty acid ester lubricants and emulsified paraffin.

7. The ultra-high density water-based drilling fluid according to claim 6, characterized in that: The lubricant is a fatty acid ester lubricant and emulsified paraffin, and the mass ratio of the fatty acid ester lubricant to the emulsified paraffin is (2-3): (1.5-2).

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