RU2277571C1 - Clayless drilling mud - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: clayless drilling mud for exposing zones with abnormally high formation pressure comprising sodium formate (13-44%) as stabilizer and weighting substance, marble powder (0-14%), and water contains carboxylmethyl-starch (3-5%) as rheological and filtration characteristics control agent. Drilling mud may further comprise foam suppressor MAS 200 dissolved in diesel fuel at ratio 1:20 and in amount 0.13-0.3%.

EFFECT: enhanced flocculation properties of drilling mud to remove sludge during cleaning operation, increased boring speed and heat resistance of drilling mud with low chemical aggression toward environment.

2 cl, 1 tbl

Description

The invention relates to the oil and gas industry, in particular to clay-free saline solutions for opening drilling zones with abnormally high reservoir pressure (AAP) by drilling.

Known clay-free drilling fluid for opening wells with abnormally high reservoir pressures, including mineralized water, as an acrylic ingredient, polyacrylamide and optionally a long-chain polymer of anionic cellulose and sodium silicate (patent RU 2170753 C2, 09 K 7/02, 07/20/2001) .

Known clayless drilling fluid system "Flo-Pro" company MI Drilling Fluids, including, wt.%: As a stabilizer, magnesium oxide - 0.4, a regulator of rheological properties - biopolymer Flo-Vis Plus - 0.5, modified starch Flo-Trol - 1.2, liquid bactericide MI Cide - 0.05, filler - marble powder - 9.0, weighting agent - potassium chloride - 3.0, the rest of the water.

However, when drilling wells in carbonate rocks, this solution is unsatisfactorily cleaned of drill cuttings, which leads to rapid abrasive wear of both bottomhole and drilling equipment on the surface, and this solution is chemically aggressive with respect to equipment and environmentally hazardous to the environment.

The closest analogue is the technological fluid for drilling, completion and overhaul of oil and gas wells in the conditions of high pressure and high temperature, including a polysaccharide reagent or a mixture of polysaccharide reagents, wt.%: 0.1 - 7.0, as a weighting agent - formic salt alkaline metal acids 45.0 - 83.0 and the rest water (patent RU 2215016 C1, 09 K 7/02, 10.27.2003).

Known process fluid does not provide the required flocculating properties of the solution.

The objective of the invention is to preserve the initial reservoir properties, reservoir strata, preservation from decompression of the rock mass, both sandstone and shale.

The technical result consists in providing high flocculating properties of the solution for removing sludge during cleaning, ensuring high drilling speeds, ensuring high heat resistance of the drilling fluid with low chemical aggression to the environment when opening the pressure drop.

Clay-free drilling fluid for opening areas with abnormally high reservoir pressure, including sodium formate, marble powder and water as a stabilizer and weighting agent, contains carboxyl methyl starch as a regulator of the rheological and filtration properties in the following ratio, wt.%: Sodium formate 13-44, carboxylmethyl starch 3-5, marble powder 0-14, water the rest. Clay-free drilling fluid may additionally contain as an antifoam MAC 200, dissolved in diesel fuel in a ratio of 1:20, in an amount of 0.13-0.3 wt.% By weight of the drilling fluid.

The causal relationship between the essential features and the technical result achieved is as follows: carboxylmethyl starch (CMC) gives the solution the necessary rheological properties and regulates water loss, and with the addition of sodium formate these properties can change, so the concentration of CMC up to 5% can be considered optimal. With an increase in the concentration of sodium formate, the thixotropic properties are enhanced, and the resulting solution is better cleaned of cuttings. Moreover, the resulting effect exists up to a concentration of sodium formate of 44%. Entering the drilling fluid antifoam MAC 200 dissolved in diesel fuel in a ratio of 1:20, it is possible to regulate the foaming process. The optimal effect is achieved at a concentration of 0.3%. If necessary, up to 14% of marble powder is added, which is inert with respect to all introduced reagents and is intended for additional weighting of the drilling fluid and the formation of a filter cake.

The composition of the prepared solution includes sodium formate / TU U Z.50-14308351-130-99 /, mass fraction 88%, mass fraction of water 0.66%. Known as a good plasticizer and preservative, it is used in construction and other sectors of the economy. The composition of the solution also includes marble powder, for example, grade MP-2 (micromarble powder TU 5716-002-369-45182-2003), manufacturer of Special Burmaterials, Moscow, carboxylmethyl starch (KMK), is widely used in well drilling (TU 2262-016-32957739-01, TU 2232-007-2957739-99), manufacturer of Special Burmaterials, Moscow, MAC 200 antifoam (TU 39-08-125-77), which is a highly dispersed fumed hydrophobized silica, manufacturer " Special materials ", Moscow.

Drilling fluid is prepared as follows.

At the required volume of clay-free drilling fluid for opening areas with an abnormally high reservoir pressure, technical water is collected, 3% of CMC is injected through the clay mixer in a cycle, not through the well, in the technical (casing) string, the fluid is replaced with the prepared solution, 13% is brought through the well sodium formate. Then, 1% CMC is introduced in a cycle and sodium formate is added, bringing the clay-free drilling fluid to the required density. In this case, sodium formate is saturated up to 44%, and the density increases to 1330 kg / m ³ . If necessary, when opening permeable rocks, up to 14% of marble powder is added, the density increases to 1450 kg / m ³ . The thickness of the filter cake can be adjusted by selecting marble powder of varying degrees of dispersion. During preparation, standard solution parameters are measured: density, conditional viscosity, dynamic shear stresses, plastic viscosity, static shear stress, water loss, pH of the medium, filter cake thickness, stickiness, etc.

The technological parameters of the solutions are given in the table. The tests performed show that changing the contents of the ingredients down (composition No. 1) does not provide the necessary technological parameters, and upward (composition No. 15) is not economically profitable, since the increased consumption of reagents does not lead to the expected effect.

Table
Composition and properties of non-clay mud Experience Number The composition of the solution, wt.% Density
kg / m ³ Conditional viscosity, sec Plastic viscosity MPa * s CSN
dpa Water loss cm ^3/30 min Sodium formate KMK Marble Powder MP-2 Antifoam MAC 200 Water one 0 3 0 0 97 1000 56 - - - 2 9.0 3 0 0 88 1050 thirty - - - 3 13.0 5 0 0 82 1070 70 - - - four 23.0 four 0 0 73 1150 90 - - - 5 30,0 four 0 0.13 65.87 1220 67 - - - 6 37.0 3 0 0.13 59.87 1270 62 - - - 7 39.0 3 0 0.24 57.76 1280 62 - - - 8 40,0 3 0 0.23 56.77 1295 63 39 134.1 - 9 42.0 3 0 0.22 55.78 1310 63 52 86.21 - 10 44.0 3 0 0.32 52.68 1330 63 53 91.0 3.2 eleven 41.0 3 6 0.32 49.68 1380 80 56 119.7 2.2 12 39.0 3 10 0.32 47.68 1400 one hundred 62 - 4.6 13 38,0 3 12 0.32 46.68 1450 95 29th 134 - fourteen 37.0 four fourteen 0.30 44.70 1450 one hundred - - -  fifteen 39.0 four fourteen 0.30 42.7 1450 115 - - 6

Claims (2)

1. Clay-free drilling fluid for opening areas with abnormally high reservoir pressure, including sodium formate, marble powder and water as stabilizer and weighting agent, characterized in that it contains carboxylmethyl starch as a regulator of rheological and filtration properties in the following ratio of components, wt.% : Sodium formate 13-44 Carboxylmethyl starch 3-5 Marble powder 0-14 Water Rest 2. The solution according to claim 1, characterized in that it additionally contains as an antifoam MAC 200, dissolved in diesel fuel in a ratio of 1:20, in an amount of 0.13-0.3 wt.% By weight of the drilling fluid.