RU2558069C1 - Method of oil well development (versions) - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: according to method of development of oil well containing oil-bearing stratum and underlying water-bearing stratum divided by bulkhead having thickness of 0.8-2m the well is surveyed in order to identify position of oil-bearing and water-bearing stratum strata. State of the flow string is defined. Behind-the-casing-flows are identified. Inflow and injection profiles are defined. Then water-bearing stratum is perforated. A packer is run down to the upper boundary of water-bearing stratum and set. Then water shutoff compound is injected and flushed to water-bearing stratum in volume precalculated as per analytic expression. Water shutoff screen is formed. Then the packer is pulled out. Cement grout is pumped to the flow string up to the level higher than roof of oil-bearing stratum until it forms a cement plug insulating the stratum. Upon waiting period for cement hardening the cement plug is drilled out up to the depth higher than roof of water-bearing stratum. At that minimum waiting period for cement hardening is equal to 24-72 hours. Tightness of the bottom hole is surveyed. The oil-bearing stratum is penetrated within the required interval and oil is recovered.

EFFECT: reduced probability of behind-the-casing flows in underlying water-bearing strata, increasing oil flow rate and reducing water encroachment in oil.

2 cl, 1 tbl, 1 dwg

Description

The invention relates to the oil industry and may find application in the development of an oil well.

At present, at the opening of the productive deposits of the Pasha horizon of the terrigenous Devonian, the geological section can be represented by several productive oil and aquifer strata, separated by clay bridges of small thickness (0.8-2 m). Small thicknesses of clay bridges between oil-saturated and aquifers are the main cause of casing flows. The elimination of behind-the-casing flows is a low success due to technological complexity.

A known method of developing a multilayer oil reservoir (patent RU 2431747 C1, IPC E21B 43/32; publ. 10/20/2011), including opening the casing string, lowering the packer on the tubing (ROST), installing the packer between the layers, injecting the hardening grouting mortar and waiting for its hardening, characterized in that the cement slurry is pre-pumped and pushed into the lower flooded formation, after the cement slurry is solidified, the casing is opened above the lower formation, the packer is installed above at the perforation interval of the casing string, and at the lower end of the tubing string, a fitting is installed for receiving fluid by the pump from the flooded formation.

The disadvantage of this method is the impossibility of its use in wells in which the oil and water bearing strata are separated by jumpers of small thickness in the range of 0.8-2 m. Thus, according to the known method, to exclude annular flows in the interval between the strata, the casing of the well is opened by perforation and the grouting is injected solution into the annular space, and the perforation interval is at a distance of two meters above the roof of the lower layer. Then between the upper layer and the perforation interval at a distance of 1.5 m above the perforation interval set the packer.

The problem to which the invention is directed is to provide a method for developing an oil well containing oil and water strata separated by small thicknesses with each other.

The technical result is to reduce the risk of casing crossflows from underlying aquifers, reducing water cut, increasing oil production and therefore oil recovery, expanding the arsenal of technical equipment.

The problem is solved by a method for the development of oil wells in which oil and aquifers are separated by bridges of small thickness (0.8-2 m), containing stages in which:

1. Carry out a well study to determine the position of the oil and aquifer, to determine the condition of the production casing.

2. Perforate the aquifer and pump and pressurize the waterproofing composition into the aquifer.

3. The cement slurry is pumped into the production casing to a level above the roof of the oil reservoir to form a cement bridge insulating the formation.

4. After the waiting time for cement hardening, drill a cement bridge to a depth above the roof of the aquifer.

5. Investigate the tightness of the face.

6. Open the oil reservoir in the required interval.

7. Carry out oil production.

In FIG. Figure 1 shows a section of a well with oil-bearing (NP) and aquifer (VP) formations separated by a bridge of small thickness (0.8-2 m).

One embodiment of the method comprises the following steps.

The amount of waterproofing composition and cement required for the work in the well is determined. The amount of waterproofing composition required to kill a waterlogged formation depends on the thickness of the formation and its permeability.

In one embodiment, the preliminary calculation of the required volume of the composition is carried out according to the formula:

V _s ≈3.14 · m · h · R ² ,

where V _s - injection volume, m ³ ;

m - coefficient of porosity, fraction of units;

h is the estimated thickness of the reservoir, m;

R is the radius of the created waterproofing screen, m

The technological packer is lowered onto the tubing to the planned planting depth (to the upper boundary of the interval of fluid (water) inflow from the well). The depth of the packer is determined with the condition of preventing the injection of the waterproofing composition into the interval of the reservoir, from which there is an influx of oil.

Next, the technological packer is planted at the planned depth with the control of the landing site by geophysical methods.

Then, the previously prepared waterproofing composition is pumped into the isolated interval through the tubing. As a waterproofing composition, a DSGA Polymer based composition (manufactured by Chevron-Phillips Lp) can be used. The following components are used in this composition:

- water-soluble polymer DSGA Polymer;

- sodium thiosulfate crystalline, corresponding to the requirements of GOST 244-76, to accelerate the dissolution of the DSGA polymer;

- sodium bichromate technical, corresponding to the requirements of GOST 2651-78, for crosslinking the solution as a gelling agent;

- potassium chloride, corresponding to the requirements of GOST 4568-95, for regulating the pH of water for dissolving polymer DSGA;

- solvent for the preparation of the waterproofing composition - fresh water or used in the PPD system (technical, formation, natural) without the presence of mechanical impurities with a pH of not more than 4. During the seasons with low ambient temperatures, it is necessary to use heated water with a temperature of 20 ° C.

An approximate composition is shown in table 1.

Table 1 Polymer grade Composition polymer concentration, kg / m ³ the concentration of sodium dichromate, kg / m ³ the concentration of sodium thiosulfate, kg / m ³ the concentration of potassium chloride, kg / m ³ DSGA Polymer four one four twenty

The gel formation time from the waterproofing composition with the composition shown in table 1 is approximately 2-6 hours. Depending on the properties of the water for dissolving the DSGA polymer, it is possible to adjust the recommended concentration ranges of the reagents. The concentration of sodium dichromate in the waterproofing composition can be reduced in order to extend the gel formation time to 5-6 hours, or it can be increased in order to reduce the gel formation time to 2-3 hours.

The water-proofing composition is pressed into the reservoir by pumping technological fluid into the tubing in a volume equal to the volume of the tubing string.

Next, you need to tear and lift the technology packer.

Then, cement mortar (plugging solution) is injected to form a cement bridge insulating the formation. For the preparation of the cement mortar, cement Portland cement can be used that meets the requirements of GOST 1581-96 "Portland cement cement. Technical conditions" or cement of other grades approved for use in the oil industry.

Leave the well at the time of gel formation from the waterproofing composition and waiting for the cement to harden (OZZ). Depending on the composition of the waterproofing composition and cement slurry used, the minimum well shut-off time for gel formation of the waterproofing composition and cement hardening can vary from 24 to 72 hours.

Investigate the tightness of the face. To do this, using pressure testing with overpressure, for example 150 atm, determine the tightness of the bottom. The pressure drop indicates the presence of a message between the face and a previously isolated formation. After pressure testing, it is necessary to reduce the level in the well by swabbing to a depth of 700-800 m, and then determine the level in the well using a geophysical instrument (thermometer, moisture meter) several times over a certain period of time. For example, such level measurements can be taken 1 hour, 2 hours, and 3 hours after swabbing. If the fluid level does not change, then the face is tight and there is no message from the underlying isolated formation.

Then drill the cement bridge to a depth above the roof of the aquifer.

The oil reservoir is opened in the required interval and the well is launched.

It is worth noting that in other embodiments, in a waterproofing composition, as a gelling polymer may be used:

- polyacrylamide (PAA) that meets the requirements of TU 2458-001-82330939-2008 "Specifications. Polyacrylamide DP9-8177".

- guar gum - galactomannan (a polysaccharide of plant origin) of the Guamine trademark in accordance with TU 2458-019-57258729-2006.

- xanthan gum (xanthan exopolysaccharide - a biopolymer of microbial origin), a solution of xanthan biopolymer (RBC).

- sodium carboxymethyl cellulose (CMC) that meets the requirements of TU 2231-002-50277563-2000 "Technical sodium carboxymethyl cellulose. Technical conditions."

As gel inducers in a waterproofing composition, the following can also be used:

- chromium acetate according to TU 2499-008-55373366-2006 "Chromium acetate, water solution" or TU 2499-001-50635131-00 "Tanning agent. Aqueous solution of chromium acetate. Technical conditions";

- Zinc oxide according to GOST 10262-73 "Reagents. Zinc oxide. Specifications." Mass fraction of zinc oxide (ZnO) not less than 99.2%;

- Magnesium oxide according to TU 6-09-3023-79 "Magnesium oxide precipitated from natural raw materials. Qualifications" pure ", or GOST 844-79" Technical burnt magnesia. Technical conditions. "Mass fraction of magnesium oxide (MgO) not less than 89%.

In yet another embodiment, the volume of the waterproofing composition for conducting work in the well is calculated based on the following empirical relationship:

V-20 + 5H;

where V is the volume of the waterproofing composition, m ³ ;

N - effective perforated thickness of the insulated interval, m

In most cases, the volume of the waterproofing composition for work in one well is 20-40 m ³ .

Instead of cement mortar, a composition based on urea-formaldehyde resin (KFS) of KFZh grade GOST 14231-88 "Urea-formaldehyde resins. Specifications" or Rezoyl K-1 TU 2221-637-55778270-2004 grade can be used as a plugging solution. "Urea-formaldehyde resin brand Rezoyl K-1."

Claims (2)

1. The method of developing an oil well containing oil and underlying aquifers, separated by a bridge with a thickness of 0.8-2 m, containing stages in which:
- carry out a well study to determine the position of the oil and aquifer, determine the condition of the production casing, identify casing flows, determine the flow profiles and injection profiles;
- perforate the aquifer;
- carry out the descent of the packer to the upper boundary of the aquifer and landing of the packer;
- carry out the injection and forcing into the aquifer of the waterproofing composition in the volume previously calculated by the formula:
V ₃ ≈3.14 · m · h · R ² ,
where V ₃ - injection volume, m ³ ;
m - coefficient of porosity, fraction of units;
h is the estimated thickness of the reservoir, m;
R is the radius of the created waterproofing screen, m;
- carry out the rise of the packer;
- pumped into the production casing cement to a level above the roof of the oil reservoir to form a cement bridge, insulating the formation;
- after the waiting time for cement hardening, drill a cement bridge to a depth above the roof of the aquifer, and the minimum waiting time for cement hardening is 24-72 hours;
- investigate the tightness of the face;
- open the oil reservoir in the required interval; and
- carry out oil production. 2. A method of developing an oil well containing oil and underlying aquifers, separated by a bridge 0.8 to 2 m thick, comprising the steps of:
- carry out a well study to determine the position of the oil and aquifer, determine the condition of the production casing, identify casing flows, determine the flow profiles and injection profiles;
- perforate the aquifer;
- carry out the descent of the packer to the upper boundary of the aquifer and landing of the packer;
- carry out the injection and forcing into the aquifer of the waterproofing composition in the volume previously calculated by the formula:
V = 20 + 5H,
where V is the volume of the waterproofing composition, m ³ ;
N - effective perforated thickness of the insulated interval, m;
- carry out the rise of the packer;
- pumped into the production casing cement to a level above the roof of the oil reservoir to form a cement bridge, insulating the formation;
- after the waiting time for cement hardening, drill a cement bridge to a depth above the roof of the aquifer, and the minimum waiting time for cement hardening is 24-72 hours;
- investigate the tightness of the face;
- open the oil reservoir in the required interval; and
- carry out oil production.

Images