RU2269000C2 - Method for permeable well zones determination - Google Patents

Abstract

FIELD: geophysical investigations, particularly oil and gas well drilling.

SUBSTANCE: method involves lowering flowmeter in well; injecting liquid and lifting the flowmeter along with continuous liquid injection. The flowmeter is suspended by elongated flexible pipes to reach horizontal bore face and then circulation is provided through hole annuity and elongated flexible pipes along with simultaneous lifting thereof to move the flowmeter over the full horizontal bore length. The flowmeter records rate of fluid flowing via the hole annuity.

EFFECT: provision of accident-free flowmeter lowering in horizontal bore due to direct determination of permeable zone boundaries in horizontal bore.

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Description

The invention relates to the drilling of oil and gas wells, and in particular to methods of geophysical exploration.

There is a method of determining permeable zones in a cased and uncased wellbore using geophysical surveys by measurements using a complex: standard logging, caliper, thermometer. However, the method does not allow to determine exactly the intervals of the permeable zones and the intensity of their injectivity [1].

The closest technical solution adopted for the prototype is a method for determining the permeable zones of the well, including the descent of the flow meter into the well, pumping fluid and raising the flow meter with continuous pumping [2].

For research, a flow meter descends on the cable and the fluid is pumped; when the flowmeter is raised, the flow rate of the fluid moving along the wellbore is measured. Data on the change in the flow rate through the cable is transmitted to the surface. By measuring the flow rate along the trunk conducted through rocks with several permeable zones, their power and location intervals are determined.

The use of flow metering using flowmeters lowered on a cable into the well is difficult in horizontal shafts, which limits its use. In horizontal trunks with a length of 300-400 m or more, especially in uncased trunks, it is practically impossible to deliver a flowmeter to their bottom. In practice, the cable is lowered along with the device, and the cable is then lowered into the annular space: between the wellbore and the tubing. Carrying out such an operation is dangerous because of the possible jamming of the cable during tripping, breaking it. As a result of this - emergency work.

In a horizontal barrel, the flowmeter is lowered to the bottom. Then they begin to pump liquid, forcing it into the permeable zones. In this case, the emulsion, sludge goes towards the flowmeter, lifted from the barrel. The resulting plugs do not allow measurements by a flowmeter.

The task is to ensure a trouble-free descent of the flow meter into the horizontal barrel.

The problem is solved due to the fact that in the method for determining permeable zones, including the descent of the flowmeter into the well, the injection of fluid and the raising of the flowmeter with continuous injection of fluid, the flowmeter is lowered on long flexible pipes to the bottom of the horizontal wellbore, then circular circulation is created through the annulus and long flexible pipes and at the same time carry out their rise to move the flow meter along the entire length of the horizontal barrel. In this case, the flowmeter fixes the flow rate of the fluid in the annulus.

Long flexible pipes (DHT) in this case are a means of delivery and transportation of the flow meter along the horizontal wellbore, as well as a channel for creating a circular circulation in the well.

The use of circular fluid circulation with different capacities allows us to establish a relationship between the flow rate of the fluid (Q) into the absorption zone and the pressure at the wellhead (P) for each of the permeable zones, i.e. determine its specific hydrodynamic characteristic.

In FIG. 1 shows a general scheme for conducting research in a well 1 with a horizontal wellbore 2, with zones of high permeability 3, into which a pipe string, for example, DHT, 4 with a flow meter 5, is lowered.

The method of flow measurement in horizontal trunks using DHT is as follows.

DHT 4 descends into an open horizontal wellbore 4 with a flowmeter 5 at their end measuring the fluid flow rate in the space between the DHT and the wellbore. In a cased column, measurement is made between the column and the DHT.

The flow meter is allowed to the bottom of the horizontal trunk (Fig. 1). A circular circulation is created. Liquid (e.g. produced water) is pumped into the annulus with a capacity of Q ₀ . The fluid flow passes through the annular space, reaches the flow meter 5 and rises through the DHT 4 to the surface with a capacity of Q _i . When passing through a horizontal trunk, the flow rate decreases as it passes from one permeable zone 3 to another. When lifting DHT 4 with a flow meter 5, the device captures the change in flow rate (figure 2) after passing through each permeable zone.

At the same time, the flow rate of the outgoing fluid from the well through DHT is recorded on the surface.

In FIG. 2, the stages in conducting research in a horizontal well using a flowmeter 5 and a hydraulic turbine 4 in the presence of 3 permeable zones (1 '; 2'; 3 ') are highlighted. In FIG. 2 marked stages "a"; "b"; “c”, respectively, after the flowmeter 5 successively passed 3 'in the process of research when lifting the gas turbine engine 4; 2 '; one'; zones.

At the beginning of the operation to study the horizontal shaft 2, when the flowmeter 5 is on the bottom, the flow of fluid pumped through the annulus is expressed as follows:

Q ₀ = Q _P + q ₁ + q ₂ + q ₃ ,

where: Q ₀ is the flow rate of the fluid pumped on the surface into the annulus;

Q _P - flow rate recorded by the flow meter at the end of the DHT;

q ₁ , q ₂ , q ₃ - flow rate of fluid flows into the permeable zone (figure 2) 1 '; 2 '; 3 ', which crossed the horizontal trunk.

In this position, the flow rate Q _P , fixed by the flow meter, is equal to the flow rate Q _i that emerges from the DHT to the surface.

When lifting DHT during the measurement of "leaks" along the horizontal trunk, Q _i will change, because only part of the flow will pass through the flowmeter. Another part of the total fluid flow will go into the permeable zones that the flow meter has passed when raising the DHT.

The value of Q _i practically remains constant during the whole process of raising DHT with a flow meter from a horizontal shaft.

In FIG. Figure 2 shows the steps for measuring fluid "leakage" into 3 permeable zones.

After passing through the 1st zone, the flow meter will show the following flow change:

Q _p1 = Q ₀ -q ₁ -q ₂

After the 2nd zone:

Q _p2 = Q ₀ -q ₁

Raising the flow meter further than the first zone, where Q _p = Q ₀ can be a control, on the basis of which the values of the "leaks" q ₁ , q ₂ and q ₃ should be refined.

An updated hydrodynamic characteristic of the permeable zones in the horizontal wellbore can be obtained if the studies are carried out repeatedly with different productivity of fluid injection from the wellhead.

The data of studies of wells with injection of fluid under pressure into permeable zones do not always coincide with the data of studies when they are carried out with depression on formations, because at elevated pressure (above reservoir pressure), for example, in fractured rocks, cracks open, and when the pressure decreases below the reservoir, part of the cracks closes.

The proposed method for determining permeable zones in horizontal shafts allows studies to be carried out both with increased pressure on the zones and with a decrease in pressure below the reservoir. To do this, aerated fluid, foam or oil is pumped into a horizontal well. At a pressure in the horizontal well below the reservoir zone, an intensive flow of fluid will occur. During a circular circulation of aerated fluid, the flowmeter will record an increase in fluid flow through the annulus. The flow will change as the flexible pipes rise from the horizontal barrel and will be fixed on a stand-alone recording device connected to the flowmeter.

The transmission of measurement data by a flowmeter can be carried out in various ways.

For example, autonomously. A recording device is built into the flowmeter. After the rise of DHT, the record is decrypted and submitted for analysis. The use of DHT provides open source software with a flowmeter in the shortest time and is not difficult in the organizational plan.

Another way to record the operation of the flowmeter may be to use a hydraulic channel. The pulsation of the flow in DHT in this case is created with the help of a rotor of the flow meter, which during rotation blocks part of the hole in the DHT.

The advantage of the proposed method is the direct physical determination of the boundaries of the zones of permeability in the horizontal wellbore by fixing changes in fluid flow when the flowmeter rises, and the presence of circular fluid circulation during research eliminates the risk of sticking the device in the well.

             Information sources

            1. Krylov V.I., Blinov G.S., Sidorov I.A., Sukhenko N.I. Complications when drilling wells. M .: Nedra, 1965, p. 27-39.

              2. Ivachev L.M. The fight against the absorption of flushing fluid while drilling exploration wells. M .: Nedra, 1982, p. 42-70.

Claims (1)

The method of determining permeable zones, including the descent of the flowmeter into the well, fluid injection and raising the flowmeter with continuous fluid injection, characterized in that the flowmeter is lowered on long flexible pipes to the bottom of the horizontal barrel, then create a circular circulation through the annulus and long flexible pipes and at the same time carry out their rise to move the flow meter along the entire length of the horizontal barrel, while the flow meter fixes the flow rate of the fluid through the annulus.

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