RU2291182C1 - Weighted drilling fluid for exposing producing formations - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: weighted drilling fluid for exposing zones with abnormally high formation pressures contains, wt %: clay 1-2, barite 10-60, sodium formate as stabilizing reagent 10-30, and carboxymethylated starch as rheological and filtration property regulator 1-5.

EFFECT: improved flocculation property of fluid, increased drilling speed, increased heat resistance of fluid, and decreased corrosion effect.

1 tbl

Description

The invention relates to the oil and gas industry, in particular to weighted drilling fluids for opening areas with abnormally high reservoir pressure (AAP) by drilling.

Known weighted drilling fluid containing clay, a stabilizing reagent - CMC, mineral salt - potassium chloride, hydroxide, plasticizer, barite, lubricant additive and water at a certain ratio of components (RU 2235751 C1, IPC7 09 K 7/02, publ. 10.09 .20040.

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.

The objective of the invention is the preservation of the initial reservoir properties, reservoir strata, preservation from decompression of the rock mass, both sandstone and shale, the possibility of its use during prolonged shutdowns of the well at low temperatures.

The technical result consists in increasing the flocculating properties of the solution for removing sludge during cleaning, drilling speeds, heat resistance of the drilling fluid with low chemical aggression to the environment during autopsy opening.

The specified technical result is achieved by the fact that the weighted drilling fluid for opening areas with abnormally high reservoir pressure contains clay, barite, a stabilizing reagent - sodium formate, carboxymethyl starch (KMK) and water, as a regulator of rheological and filtration properties, in the following ratio of components , wt.%: clay - 1-2, barite - 10-60, sodium formate - 10-30, KMK - 1-5, water - the rest.

The causal relationship between the essential features of the invention and the achieved technical result is as follows. As a stabilizing reagent, sodium formate is used, a regulator of the rheological and filtration properties of KMK, which 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 KMK - 1-5% 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 30%. In turn, sodium formate is used as an excellent reagent - stabilizer for a weighted solution, as well as a shale inhibitor reagent, however, the maximum effect exists only at the stated concentrations and combinations.

The composition of the solution includes sodium formate, formic acid salt, may be in the form of a yellow-white or gray powder, produced according to TU 2432-011-00203803-98 CJSC Metafraks, mass fraction 88%, water mass fraction 0.66% , known as a good plasticizer and preservative, is used in construction and other sectors of the economy. Clay and barite (GOST4682-84) are widely used in solutions in well construction; they are produced by Ural Bentonites; as well as modified starch-carboxymethylated starch (KMK), the supplier of Spetsburmaterialy CJSC, is widely used in well drilling (TU 2262-016-32957739-01, TU 2232-007-29577739-99).

The solution is prepared as follows.

At the required volume of weighted drilling fluid for opening areas with abnormally high reservoir pressure, technical water is collected, through the clay mixer, 1-5% CMC is not introduced through the well through the cycle, then clay is added no more than 2%. Barite is weighted to a density of 1600 kg / m ³ , sodium formate 10-40% is added.

During preparation, standard solution parameters are measured: density, nominal viscosity, dynamic shear stress, plastic viscosity, static shear stress, water yield, pH of the medium, filter cake thickness, stickiness, etc.

The table shows the compositions and parameters of drilling fluids. The tests performed show that changing the quantitative content of the components down (composition No. 1) does not provide the necessary technological parameters, and upward (composition No. 6, 7) is not economically profitable, since sodium formate with a concentration of over 30% reaches saturation and increased consumption of reagents does not match the expected effect.

Table Solution composition Solution parameters Composition number Sodium formate
wt.% KMK, wt.% Clay, wt.% Barite, wt.% Water, wt.% Density,
kg / m ³ Conditional viscosity
from Plastic
viscosity
MPa · s DNS dPa SNA
1 min/
10 min
dpa
/ DPa Water loss
cm ^3/30 min one 9 one 0 9 81 1075 eighteen - - - - 2 10 2,5 one 10 76.5 1090 37 34 77 15/96 3.2 3 twenty 6 2 48 24 1700 134 64 181 15/51 0.5 four thirty 5 2 48 fifteen 1700 68 56 - 18/60 1,0 5 twenty 2,5 2 60 15,5 2100 67 - - - - 6 twenty 2,5 2 61 14.5 2100 62 - - - - 7 31 2,5 3 34 29.5 1700 n / t - - - -

Claims (1)

Weighted drilling fluid for opening zones with abnormally high reservoir pressure, containing clay, barite, sodium formate as a stabilizing reagent, and carboxymethylated starch and water as a regulator of rheological and filtration properties, in the following ratio, wt.%: Clay 1-2 Barite 10-60 Sodium formate 10-30 Carboxymethyl starch 1-5 Water Rest