RU2728910C1 - Drilling mud for well construction under conditions of abnormally high formation pressures and high temperatures - Google Patents

Abstract

FIELD: construction.SUBSTANCE: invention relates to construction of oil and gas wells. Drilling mud for well construction under conditions of abnormally high reservoir pressures and high temperatures includes, wt. %: xanthane biopolymer 0.08–0.22; starch reagent 0.28–0.76; lignosulphonate 0.30–0.82; potassium chloride 2.38–6.56; potassium formate 8.06–22.18; ground marble 1.98–5.46; barite filler to 63.70; water 23.22–63.92.EFFECT: technical result is high sedimentation stability at high temperatures and possibility of weighting drilling fluid to density of 2_30 g/cm, thermal stability up to 150 °C, high inhibiting power of clay hydration, resistance to biodegradation, good lubricating properties.1 cl, 1 dwg, 4 tbl

Description

The invention relates to the construction of oil and gas wells, in particular to water-based drilling fluids used in construction, completion and workover of wells in conditions of abnormally high reservoir pressures and elevated temperatures.

Known drilling fluids intended for construction of wells in conditions of abnormally high reservoir pressures and temperatures, containing alkali metal formates as a weighting additive (patents: RU 2215016, RU 2277570, RU 2277571, RU 2655276).

The disadvantages of these drilling fluids are their insufficient density (RU 2277570, RU 2277571) and / or high structural and rheological properties (RU 2215016, RU 2655276), which is associated with a high content of formate - 37.00-83.00 wt. % depending on the required density of the solution.

The composition of the drilling fluid according to the patent RU 2215016, wt. %:

Polysaccharide reagent or mixture of polysaccharide reagents 0.10-7.00 Formic acid salt alkali metal 45.00-83.00 (solution density 1.35-2.30 g / cm ³ ) Water Rest

The composition of the drilling mud according to the patent RU 2277570, wt. %:

Sodium formate 9.00-44.00 (solution density up to 1.42 g / cm ³ ) Fito-PK polymer 3.00-5.00 Marble powder 0.00-10.00 Water Rest

The composition of the drilling fluid according to the patent RU 2277571, wt. %:

Sodium formate 13.00-4.00 (solution density up to 1.45 g / cm ³ ) Carboxylmethyl starch 3.00-5.00 Marble powder 0-14.00 Water Rest

The composition of the drilling fluid according to patent RU 2655276, wt. %:

Sodium formate 37.00-42.00 Xanthan-type polysaccharide 0.27-0.32 Modified starch 0.84-1.06 Water repellent liquid 0.69-1.01 Lubricating additive 1.63-1.97 Galena weighting compound over 100 wt. % (solution density up to 1.90-2.60 g / cm ³ )

Known drilling mud containing as the main weighting additives potash or sodium formate, marble powder for weighting and clogging, barite weighting agent for additional weighting to the required density (patent RU 2440397).

The composition of the drilling fluid according to the patent RU 2440397, wt. %:

Organic acid alkali metal salt - potash or sodium formate 10.00-50.00 (the achieved solution density is 1.22-1.80 g / cm ³ ) Biopolymer KK Robus 0.40-0.45 Modified starch KREM 1.00-1.10 Water repellent liquid Osnova-GS 0.25-0.30 Complex lubricant additive KSD 1.00-1.50 Water 87.35-46.65 Marble powder 30.00-65.00 over 100 Barite weighting agent up to 65.00 over 100

In the known drilling fluid (patent RU 2440397) sodium formate is used in large quantities and as the main weighting additive. The maximum density of the solution is 1.60-1.80 g / cm ³ with the content of sodium formate 40.00-50.00 wt. %.

The main disadvantages of this drilling mud are insufficient maximum density and high content of sodium formate, which leads to an increase in the cost of the mud and deterioration of the structural and rheological properties.

The closest to the claimed technological solution is a drilling mud (RU 2291182) containing 1.00-3.00% clay, 10.00-60.00% barite, as a stabilizing reagent 10.00-30.00% sodium formate , as a regulator of rheological and filtration properties of 1.00-5.00% carboxymethylated starch, and water - the rest. This drilling fluid is designed for drilling into zones with abnormally high reservoir pressures. Known drilling mud, according to the patent holder, has increased flocculating properties for removing cuttings during cleaning, drilling rates and heat resistance when opening zones with abnormally high reservoir pressures.

The disadvantages of this drilling mud are high structural and rheological properties, in particular, high plastic viscosity.

Abnormally high reservoir pressures are often accompanied by elevated reservoir temperatures and minimal differences between the gradients of reservoir pressure and fracture pressure. For these reasons, the used drilling fluid must have, in addition to high density and thermal stability, also low hydraulic resistance to flow.

The known drilling mud does not provide the necessary structural and rheological properties for well construction in conditions of abnormally high reservoir pressures (Table 2).

Table 1 shows the concentration of ingredients in the claimed and known drilling fluids.

Table 2 shows the parameters of the drilling mud, measured in the reproduced formulations presented in the prototype patent, and the parameters of the claimed drilling mud. From the data in Table 2 it can be seen that the known drilling mud has unsatisfactory structural and rheological properties.

The objective of the invention is to create a drilling fluid with high density and heat resistance, high inhibiting ability, with rheological properties, allowing well construction to be carried out under conditions of a minimum difference between the gradients of reservoir pressure and hydraulic fracturing pressure.

The technical result achieved by the present invention is to ensure trouble-free well construction under conditions of abnormally high reservoir pressures, due to obtaining optimal structural and rheological properties of the barite-weighted drilling fluid, achieved with the combined use of potassium formate and potassium chloride, high density and thermal stability of the drilling fluid, sedimentation stability and high inhibiting ability of the drilling fluid in relation to the process of hydration of clays, resistance to biodegradation and good lubricating properties.

The specified technical result is achieved in that the solution includes polysaccharide polymers and lignosulfonate, barite weighting agent, ground marble, potassium formate, potassium chloride with the following content of components, wt. %:

Xanthan biopolymer - 0.08-0.22 Starch reagent - 0.28-0.76 Lignosulfonate - 0.30-0.82 Potassium chloride 2.38-6.56 Potassium formate - 8.06-22.18 Ground marble - 1.98-5.46 Barite weighting agent - up to 63.70 Water - 23.22-63.92

Potassium formate in an optimal concentration provides sedimentation stability and thermal stability of the properties of the solution up to 150 ° C, in addition, potassium formate gives the solution a high inhibitory ability in relation to the process of hydration of clays and good lubricating properties. Optimizing the potassium formate content also allows for a low cost of the drilling fluid. Low hydraulic resistance to the flow of the solution is achieved through the use of xanthan biopolymer and starch reagent, which impart pseudoplastic properties to the solution, in which the viscosity of the solution decreases with an increase in the shear rate, due to which the solution has a high retention and carrying capacity. To reduce the hydraulic resistance of the solution, which increases with the addition of potassium formate, the addition of potassium chloride is included in the solution, which effectively peptizes the solution and reduces the negative effect of potassium formate on the structural and rheological properties of the barite solution.

The composition of the claimed solution includes chemical reagents presented in table 3.

The composition of the claimed drilling fluid is shown in Table 4.

FIG. 1 shows a combined diagram for determining the content of barite weighting agent and water in the claimed drilling fluid of the required density.

Sources of information:

1. RU 2215016, 11.03.2002, C09K 7/02, publ. 27.10.2003 Bull. No. 30;

2. RU 2277571, 06.12.2004, C09K 8/08, publ. 10.06.2006 Bul. # 16;

3. RU 2277570, 26.11.2004, C09K 8/04, publ. 10.06.2006 Bulletin No. 16;

4.RU 2655276, March 29, 2017, C09K 8/20, publ. 05.24.2018 Bulletin No. 15;

5. RU 2440397, March 29, 2017, C09K 8/08, publ. 01/20/2012 Bulletin No. 2

6. RU 2291182, 28.06.2005, C09K 8/20, publ. 10.01.2007 Bulletin No. 1

Claims (2)

Drilling mud for well construction in conditions of abnormally high reservoir pressures and elevated temperatures, including polysaccharide polymers and lignosulfonate, barite weighting agent, ground marble, potassium formate, potassium chloride with the following content of components, wt%: Xanthan biopolymer 0.08-0.22 Starch reagent 0.28-0.76 Lignosulfonate 0.30-0.82 Potassium chloride 2.38-6.56 Potassium formate 8.06-22.18 Ground marble 1.98-5.46 Barite weighting agent up to 63.70 Water 23.22-63.92

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