RU2393339C1 - Method of development of gravel envelope in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method of development of gravel envelope in the well involves opening of productive formation with perforated casing string, wash of gravel to the space of casing string in perforation interval and to the space of cavities after the casing string with hydraulic sealing of bottom-hole formation zone (BFZ). In order to eliminate the disturbance of compact structure of sand in BFZ with formation of the cavity around the well bore owing to edging of formation sand from the well bore with further formation of compacted structure in BFZ, first, high-viscosity liquid - crosslinked gel is pumped under pressure to the formation. Then to the formed cavity and to the well bore there wound under pressure is gravel filling from high-permeability inwash fraction serving as sand filter for productive formation during operation of the well, which is made from polymer-coated material with density exceeding the density of formation sand at least by 3.5 times. At that, there simultaneously met is the condition as per the composition of gravel filter depending on particle size distribution of formation sand in compliance with Saucier criterion, according to which the median diametre of fraction particles of the filtering screen shall be more than that of formation sand by 5-6 times.

EFFECT: reducing the costs for inwash of the envelope and time for lowering-and-lifting operations.

3 cl, 1 dwg

Description

The invention relates to the oil and gas industry in the field of sand control in productive oil, gas and water wells.

A known method of creating a gravel downhole filter (see A.S. No. 1488443, publ. 06.23.89, Bull. No. 23), which consists in the introduction of gravel filling, placed between the wall of the well and the filter frame, and in its seal, when In this case, the introduction of gravel filling is carried out in batches with porosity and / or density varying in height of the filter. Between portions of gravel backfill, layers of gravel of finer fractional composition are introduced. Its compaction is carried out throughout the introduction process with an additional compaction of each previous portion of gravel before entering the next.

The disadvantages of the method are the lack of the possibility of uniform deposition of each portion of gravel backfill on the rock in the bottomhole formation zone (PZP) in an even layer due to the unpredictability of the distribution of the suspension over the formation during pumping, due to the formation of sand barriers on the way of movement, the presence of natural channels, etc.

There is another way to create a gravel filter in the well (A.S. No. 1507958, publ. 09/15/89, Bull. No. 34), including opening the reservoir with a perforated casing string, lowering the filter to trap gravel and installing it in the casing perforation interval columns, washing the gravel into the annular space between the filter and the casing and into the space of the caverns behind the casing.

Before lowering and installing the filter in the well, first they lower it into the casing string, then repeatedly seal the bottom-hole zone by pumping pulp with granular material into the filling casing, push the pulp into the bottom-hole zone at pressures equal to the fracture pressure, and then close the wellhead and withstand until the pressure on the mouth decreases to zero, after which gravel is washed. And then carry out the descent and installation of the filter in the well.

This method has the disadvantage that the injection pressure during reclining can increase sharply and disrupt the execution of the planned reclaim program, which leads to a decrease in well flow rates and is of high cost.

The proposed method of creating a gravel filter in a well, including opening a productive formation with a perforated casing string, washing gravel into the space of the casing string in the perforation interval and into the space of cavities behind the casing with hydraulic sealing of the bottomhole formation zone (PPP), in contrast to the prototype for eliminating structural compactness sand in the bottomhole formation zone with the formation of a cavity around the wellbore due to the displacement of formation sand from the wellbore with the subsequent formation of a compacted structure in the bottomhole zone in the beginning, a highly viscous fluid — a crosslinked gel — is pumped under pressure into the formation, and then a gravel bed of a highly permeable filling fraction, which serves as an anti-sand screen for formation sand during well operation, is made of a polymer-coated material with a density in the formed cavity and in the well bore; exceeding the density of the formation sand by at least 3.5 times, while simultaneously fulfilling the condition for the composition of the gravel filter, depending on the particle size distribution of the formation sand in In accordance with the Socier criterion, according to which the median particle diameter of the filter screen fraction should be 5-6 times larger than the median diameter of the formation sand, the compacted state of the sand screen filter is ensured by the creation of a filling pipe string with a design force for a given period of time through a column fixed at the end of the column heels of elastic material on a glass filled with gravel backfill, placed in the wellbore from artificial bottom to a depth of 2-5 meters above the upper perforation holes, forming e cavities around the wellbore in the bottomhole formation zone, the introduction of gravel backfill from the high-density filter fraction and into the wellbore, the creation of pressure on the gravel backfill in the wellbore, as well as the final flushing of the well from mechanical impurities, is performed in one round trip.

The drawing shows the design of the downhole filter, where the positions indicate the following:

1 - well; 2 - a column of filling pipes; 3 - heels of elastic material; 4 - layer; 5 - anti-sand filter screen in the cavity around the wellbore 1; 6 - a glass of gravel filling in the wellbore.

The method is as follows.

A casing pipe 2 is lowered into a well 1 filled with a working fluid that balances the reservoir pressure, then a highly viscous fluid is pumped under pressure into the reservoir — a crosslinked gel, which, in order to eliminate the violation of the compact structure of sand in the BCP, pushes the formation sand from the wellbore with the formation of a cavity around the trunk wells and subsequently a compacted structure in the bottomhole formation zone. Then, in the formed cavity 5 and in the well bore, gravel filling from a highly permeable wash fraction serving as an anti-sand screen for formation sand during well operation is washed under pressure. The wash fraction consists of a polymer-coated material with a density exceeding the density of the formation sand by at least 3.5 times. In this case, the condition on the composition of the gravel filter should be satisfied depending on the granulometric composition of the formation sand in accordance with the Socier criterion, in which the median particle diameter of the filter-screen fraction should be 5-6 times larger than the median diameter of the formation sand.

After the completion of the washout, a glass is compacted from gravel filling in the wellbore, located at a height from artificial bottom to a depth of 2-5 meters above the upper perforation holes. To do this, create pressure with the calculated force on the glass of the column of casting pipes 2 through the heel 3 of elastic material fixed at the end of the column, withstand for a predetermined time, after which the load is released. Then, the well is finally washed from solids.

After completion of the work, lifting pipes are lifted and the well is put into operation.

Thus, the method has significant advantages, compared with other methods, in reducing the cost of the operation, requiring expensive equipment, several tripping, significant time and other costs. The technology of using a filter screen reliably blocks the path of sand; the compact structure of formation sand in the bottomhole formation zone and the reclaimed fraction are a reliable barrier against sand formation.

Claims (3)

1. A method of creating a gravel filter in a well, including opening a productive formation with a perforated casing string, washing the gravel into the space of the casing string in the perforation interval and into the cavity space behind the casing with hydraulic sealing of the bottomhole formation zone (PPP), characterized in that to eliminate compactness sand structures in the bottomhole formation zone with the formation of a cavity around the wellbore due to the displacement of formation sand from the wellbore followed by the formation of a compacted structure in the bottomhole zone, first under a highly viscous fluid — a crosslinked gel — is pumped onto the formation, and then a gravel filling from the highly permeable filling fraction serving as an anti-sand screen for the formation sand during the operation of the well is made of a polymer-coated material with a density exceeding the density of the formation in the formed cavity and in the well bore under pressure sand, at least 3.5 times, while simultaneously fulfilling the condition for the composition of the gravel filter, depending on the particle size distribution of the formation sand in accordance with Sosier criterion, according to which the median particle diameter of the filter screen fraction should be 5-6 times larger than the median diameter of the formation sand. 2. The method according to claim 1, characterized in that the compacted state of the anti-sand filter screen is provided by creating, with a design effort for a given period of time, a column of casting pipes through a heel of elastic material fixed to the end of the column onto a gravel-filled glass placed in the wellbore from artificial slaughter to a depth of 2-5 m above the upper perforation holes. 3. The method according to claim 1 or 2, characterized in that the formation of a cavity around the wellbore in the bottomhole formation zone, the introduction of gravel backfill from the high-density fraction of the filter screen into the cavity around the wellbore and into the wellbore, creating pressure on the glass of gravel backfill in the wellbore, as well as the final flushing of the well from mechanical impurities, is performed in one round trip.

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