RU2121564C1 - Device for well swabbing - Google Patents

Abstract

FIELD: oil producing industry; may be used in completion of oil wells by swabbing and for investigation of unsteady-state processes in formations during well shut-in and renewal of well operation. SUBSTANCE: device is made in the form of downhole instrument having swab and measuring module. Swab has base of several interconnected rod mandrels with longitudinal channels-grooves on generating lines. Installed above each rod mandrel for moving up and down to stop is set of collars. Located above collars are protective wire scrapers. Measuring module includes two pressure pickups, cable tension transducer and mechanical amplifier electrically connected with them. One of pressure pickups is located for measuring of pressure of fluid filling the well above swab, while the other pressure pickup is installed under swab. Cable tension transducer connects swab with cable lug and is the main load-carrying member of swab suspension. EFFECT: higher efficiency and operating reliability of device in investigation of unsteady-state processes in formation and continuous control of cable tension, and simplified design of device. 4 dwg

Description

 The invention relates to the oil industry and can be used to study unsteady processes in the reservoir during shutdown and start-up of a well, in particular, when developing oil wells by swabbing, i.e., lowering the liquid level in them using a special piston (swab), lowered into the well on a cable or wireline.

 A device (swab) is known for swabbing oil wells [1], which consists of the following main nodes, counting from top to bottom: a metal rod connected by a special lock to a cable and used to weight the device, a valve cage with a ball valve, a hollow pipe and installed on a cuff made of a rubberized strap.

 When the swab is lowered into the well through tubing (tubing), the ball valve is open, which allows the swab to plunge into the well. When lifting, the valve closes and the entire column of liquid located above the swab is captured by the cuff, rises to the mouth and is carried to the surface.

 With continuous swabbing, the fluid level in the well decreases and, accordingly, the pressure at the bottom of the well decreases, which causes an influx of fluid from it into the reservoir.

 The main disadvantage of the considered device is the lack of control over the swabbing process by such parameters as the difference in fluid pressure above and below the swab, as well as cable tension control, since the device is a purely mechanical means of causing inflow from the formation and does not contain sensors and devices for measuring these parameters.

 Another disadvantage is that the shape of the used rubber cuffs in the form of a cylindrical ring does not contribute to the effective lifting and removal of the liquid column from the well.

 Finally, the design of the check valve is not reliable enough, since it does not exclude the possibility of its clogging and clogging with paraffin, sludge, etc., which can lead to complications during the work.

 A known device for well development by swabbing [2], including a swab and a measuring module located underneath.

 The swab contains a base in the form of a hollow cylindrical body mechanically connected from below to the head of the container of the measuring module, and from above to the logging head. Inside the housing there is a logging cable passed through the swab head. The cable electrically and mechanically connects the measuring module to ground-based instrumentation and equipment. Outside, a safety valve is mounted on the housing, spring-loaded from below, and the spring stiffness can be adjusted with a special nut. On top of the safety valve is closed by a shutter, which is rigidly fixed to the housing. The safety valve with the help of a nut that regulates the stiffness of the spring can be calibrated for the opening force, the value of which is less than the tensile strength of the cable. A gasket in the form of a cylindrical ring is installed on the safety valve. The safety valve and its shutter are equipped with interconnected passage channels, the outlet of which on the shutter is equipped with ball valves spring-loaded from above. The shutter body also has additional bypass channels.

 The measuring module contains sensors and devices for monitoring the swabbing process.

 The main disadvantage of the device is the impossibility of an effective study of transient processes in the reservoir, for example, by changing the difference in fluid pressure under the swab and above it, since the entire measuring module is under the swab, there are no measurements over the swab, and therefore it is unclear why the pressure changes under swab, due to the flow of fluid from the reservoir or due to the flow of the raised fluid through the sealing cuff. This disadvantage is compounded by the fact that the form of the cuff in the form of a cylindrical ring used in the device does not provide an effective grip and lift of the liquid column above the swab.

 Another disadvantage is that when the safety valve springs are clogged with foreign objects, sludge, etc. set to open at a certain force, the valve may not work. This, in turn, can lead to cable breakage, which is unacceptable.

 Finally, the design of ball valves is not reliable enough, since it does not exclude the possibility of their clogging and clogging with paraffin, sludge, etc., which is fraught with complications during work.

 The closest to the proposed technical solution in its technical essence and the achieved technical effect is a device for well development by swabging [3], which we adopted as a prototype.

 The device includes a swab mounted on a cable and a measuring module placed under it, which is electrically and mechanically connected to the ground equipment and equipment using a cable.

 The swab contains a base in the form of a hollow cylindrical body on which a sealing collar is mounted, embedded inside the leaf plate frame of the spring type with lower and upper rings. The lower ring is spring-loaded from below, and the upper one is from above, and the stiffness of the springs is adjusted using special nuts mounted on the housing. A safety valve is placed inside the housing, which includes a seat made on the inner surface of the housing and a shutter rigidly mounted on the upper ring and having an axial hole for cable passage. The housing and the lower adjusting nut are provided with windows for fluid circulation. In the upper end part of the housing there is a mounting unit for fixing the position of the swab on the cable, which contains a support washer rigidly fixed inside the housing, wedge slips and a clamping nut, with which the force of the cable girth is controlled by the slips.

 The measuring module contains pressure sensors, fluid composition and flow.

 The main disadvantage of this device is the impossibility of studying unsteady processes in the reservoir, for example, by changing the pressure difference under the swab and above it, since, firstly, there are no pressure measurements over the swab, and, secondly, when the swab stops (which required for such a study) a gap is formed between the cuff and the tubing wall, through which the liquid to be lifted rushes down and thus the pressure under the swab changes not only due to the flow of fluid from the reservoir, but also due to the flow of the Liquids.

 Another disadvantage is that when sludge, paraffin and foreign objects get into the springs, the safety valve does not work both for opening and closing, which can lead to cable breakage or loss of the device’s performance.

 Finally, the mount that secures the swab to the cable is not reliable enough. Significant cuff loads that occur when lifting the device can cause the swab to move down the cable, i.e. to the loss of its performance.

 In general, the considered design of the device is quite complex and not reliable enough. This applies, first of all, to the adjustment system for the necessary clearance between the cuff and the tubing wall, depending on the diameter of the tubing during descent and the required cuff pressure against the tubing wall during lifting, as well as the valve system.

 The purpose of the invention is to increase the efficiency and reliability of the device by providing the possibility of studying transient processes in the reservoir and continuous monitoring of cable tension, as well as simplifying the design.

 This goal is achieved by the fact that in the device for swabbing a well, comprising a swab base with a through axial bore and a sealing element mounted on it, and a measuring module containing a pressure sensor mounted to measure fluid pressure under the swab, the swab base is made in the form of a system of several interconnected rod mandrels with longitudinal channels-grooves connected along the generatrix, the sealing element consists of sets of cuffs installed on each of the bearings ok with the ability to move up and down to the stop, and the measuring module is additionally equipped with a second pressure sensor installed in the adapter housing above the swab, a multichannel amplifier in a protective casing and a cable tension sensor located above the swab and electrically connected to the multichannel amplifier located at the upper end part of the container is rigidly fixed to the adapter connecting the cable tension sensor to the protective casing of the multi-channel amplifier, and the lower end part tainer is mounted for free movement relative to the adapter connecting the cable tension sensor with a swab.

 In FIG. 1 and 2 show the layout of the main nodes of the proposed device; in FIG. 3 - design swab used in the proposed device; in FIG. 4 - design of the cable tension sensor and its connections with the swab and the protective cover of the measuring module.

 The device is made in the form of a downhole tool containing swab 1 and measuring module 2.

 Swab contains a base of several interconnected sections (one section is conventionally shown), each of which includes a rod mandrel 3 with channels-grooves 4, made along the generatrix, and axial holes 5 along the entire length. On each of the mandrels 3 there is a set of rubber cuffs 6 with the ability to move up and down to the stops 7, and above the cuffs on a special clip 8 protective wire scrapers 9 are placed, moving together with the cuffs 6 up and down.

 The measuring module 2 includes two pressure sensors, an upper 10 and a lower 11, a cable tension sensor 12 and a multi-channel amplifier 13 electrically connected to them.

 There are two options for placing the lower pressure sensor 11, namely, under the swab 1 (Fig. 1) and above it (Fig. 2). In the first case, the axial hole 5 is sealed and used to lay electrical communication lines from the sensor 11 to the measuring module 2. In the second case, the axial hole is depressurized and used as a hydraulic communication channel of the sensor 11 with the borehole fluid under the swab 1. However, in both cases, the lower sensor 11 will installed with the ability to measure fluid pressure under swab 1.

 The cable tension sensor 12 is housed in a container 14, which hermetically protects the sensor from environmental influences. The upper end part of the container 14 with the help of a thread is rigidly fixed to the adapter 15 connecting the cable tension sensor 12 with the protective casing of the multi-channel amplifier 13 and then through the adapter 7 with a cable lug. The lower end part of the container 14 can freely move relative to the adapter 6, connecting the cable tension sensor 12 to the swab 1. Thus, the cable tension sensor through the adapter 15, 16 and 17, the protective casing of the multi-channel amplifier 13 connects the swab 1 to the cable lug 18.

 For mechanical and electrical connection of individual parts of the downhole tool, standard connecting, load-bearing and protective elements, nodes and parts of logging equipment are used.

 The upper pressure sensor 10 is placed in the housing of the adapter 15 with the ability to measure the pressure of the liquid above the swab.

 The device operates as follows.

 When lowering the cuff 6 into the well together with the clip 8 for wire scrapers 9 under the action of the oncoming fluid flow filling the well, the mandrels 3 go up to the stops 7, opening the longitudinal channels-grooves 4 for the passage of fluid and providing free descent of the device into the well to a predetermined depth . In this case, the cable tension sensor 12 in the event of a sudden stop of the device due to a encountered obstacle signals this to the operator by reducing the amount of cable tension. Stopping the device would have gone unnoticed if a conventional tension sensor were used to measure the tension, mounted on the block balance frame at the wellhead, since the weight of the cable lowered into the well is many times the weight of the downhole tool. This, in turn, would inevitably lead to a bypass of the cable and could cause undesirable complications during operation up to the occurrence of an emergency.

 When lifting the cuff 6, under the influence of the pressure of the liquid column above the swab 1, they lower down along the mandrels 3 down to the stops 7, blocking the longitudinal channels-grooves 4 and ensuring the capture and lifting of the liquid column above the swab 1. In this case, the pressure sensor 10 registers the amount of liquid pressure above swab 1, and the pressure sensor 11 is underneath. The pressure above the swab 1 first reaches a maximum value equal to the weight of the raised liquid column, and then slightly decreases due to leakage of liquid down through the gap between the cuffs 6 and the tubing stack. The pressure under the swab 1 at the first moment drops to a minimum value, and then is gradually restored due to the pressure of the fluid entering the well from the formation. A cable tension sensor 12, on which the entire downhole tool is actually suspended, together with a raised column of liquid, detects the true value of the cable tension and, in case of exceeding the permissible values, signals this to the operator. Protective scrapers 9 during the lifting process capture and entrain foreign objects and cuttings from the well, protecting the cuffs 6 from premature wear.

 Monitoring the change in the pressure difference above and below the swab during swab allows you to examine the unsteady processes in the reservoir when shutting down and starting up the well by the pressure recovery rate, and also influence these processes by adjusting the swab mode (changing the swab's lowering depth during repeated descents and ascent speeds) .

 Cable tension control makes it possible to avoid cable bypass when moving downward when the device suddenly stops, which is not possible using a conventional tension sensor installed on the block balance frame at the wellhead, as well as cable breakage when moving upward.

 When changing the diameter of the tubing, thanks to the collapsible design of the device, it is easy to install cuffs and scrapers in the swab of the required size.

Sources of information
1. Muravyov V.M., Operation of oil and gas wells. - M .: Nedra, 1973, p. 126, 150-151.

 2. SU 1500765 A1, E 21 B 43/00, 08/15/89.

 3. SU 1686 137 A1, E 21 B 43/25, 10.23.91.

Claims (1)

 A device for swabing wells, comprising a swab base with a through axial hole and a sealing element mounted on it, and a measuring module comprising a pressure sensor mounted to measure fluid pressure under the swab, characterized in that the swab base is made in the form of a system of several connected between a bar of mandrels with connected along the forming longitudinal channels-grooves, the sealing element consists of sets of cuffs installed on each of the mandrels with the possibility of up and down movements, and the measuring module is additionally equipped with a second pressure sensor installed in the adapter housing above the swab, a multi-channel amplifier in a protective casing and a cable tension sensor located in the container mounted above the swab and electrically connected to the multi-channel amplifier, while the upper end the container part is rigidly fixed to the adapter connecting the cable tension sensor to the protective casing of the multi-channel amplifier, and the lower end part of the container is installed with the possibility of free movement relative to the adapter connecting the cable tension sensor with a swab.

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