Horizontal Wells

This invention relates to hydrocarbon production and can be used in the operation of wells, more specifically, for achieving a uniform fluid inflow rate along horizontal wells.

For the purposes of this application, the term "well completion" (see E.M. Soloviev, Well Completion, Handbook for higher educational institutions, Moscw, Nedra, 1979; Well Completion Theory and Practice, 5 volumes, A.I. Bulatov, P.P. Makarenko, V.F. Budnikov et al., Moscow, Nedra, 1997-1998, vol. 1-5) shall mean installing pipe assemblies into the well, possibly filters (for liquid flow) or future perforation, packers (insulating elements) and landing units (fastening devices (anchors) fixing the assembly in the required position).

Currently, the oil and gas industry has two main types of inflow control systems with well completion. The commonly used inflow control systems are passive devices installed in sand filters. Nozzle or pipe/channel system modifications are the most widespread ones. These systems use hydraulic impedance to develop a certain pressure drop between the formation and the well thereby changing the pressure drawdown upon the formation. The level of hydraulic impedance (set by selecting a certain diameter of the nozzle or the length and diameter of the pipe/channel system) is selected based on log data obtained after drilling or logging while drilling (LWD) data and obviously this parameter cannot be changed after equipment has been installed into the well. The main disadvantage of such systems is the lack of capability of changing their settings if the parameters of the near wellbore zone formation change in time or limiting the inflow of water or gas in case of their breakthrough. If the system is installed incorrectly or lowered to an insufficient depth, the entire assembly will fail to match the liquid inflow along the horizontal well thus deleteriously affecting the well rate and the overall oil field production.

Also known are active systems with hydraulically controlled valves that are installed on the production pipe inside the completion or the sand screens. These valves allow controlling the throttling for each zone from the ground. The main disadvantages of such systems are the high cost of equipment and servicing works during installation and operation, limited lowering depth and low reliability of operation.

Known (SU Inventor's Certificate 1733625, publ. 1992) is a set of equipment for controlling the X-trees of underwater wells comprising a main delivery pipeline, auxiliary delivery pipelines connected with hydraulic servos through the main and auxiliary hydraulic distribution valves, control lines, hydraulic reservoirs connected with the main and auxiliary delivery pipelines, pressure switches and back valves and additionally equipped with a pressure boost unit with low and high pressure chambers, wherein said control lines are connected with said low pressure chambers and the main delivery pipeline through an auxiliary hydraulic distribution valve, and said auxiliary delivery pipeline and connected with said high pressure chambers and the main delivery pipeline through said back valves, further wherein the auxiliary delivery pipeline section between the back valve and the auxiliary hydraulic reservoir have parallel pressure switches installed in parallel and connected with the auxiliary hydraulic reservoir.

The main disadvantage of said known system is the lack of capability of modifying its settings during well operation. Further disadvantages of said known system include its relatively low reliability that does not provide for the required trouble-free operation of oil wells, due to the partial or complete absence of the required polyvariant system redundancy initiating fast automatic cutoff of the produced fluid and increasing the reliability of well protection and preventing emergencies at early well operation stages by controlled remote or manual well cutoff.

Known (RU Patent 2042788, publ. 1995) is a valve device for pumping wells comprising a hollow case with input openings, a controlling element in the form of bellows installed in the top part of the case and, jointly with the case, forming a chamber filled with compressed gas and equipped with a charging unit, spring-loaded saddles located in the bottom part of the case and a stem rigidly connected at its top end with the elastic component and at its bottom end, with the gates. Said known device is used for adjusting the dynamic level of liquid in pumping wells. A disadvantage of the device is the low reliability of its operation.

Also known (SU Inventor's Certificate 1781416, publ. 1992) is a downhole plant comprising a seating nipple lowered into the well on the piping string and fitted with a detachable control valve and a cutoff device for pumping operation, said seating nipple consisting of a hollow case with passage openings, outer seals and a retainer in which bellows are installed vertically with a limited up/down stroke, rigidly connected at the bottom end with the stem and at the top end with the case and forming, jointly with the case, a charging chamber, a saddle rigidly mounted in the case and a gate under the saddle rigidly connected with the bellows stem.

A disadvantage of said known technical solution is its low reliability cause by the fact that the cutoff valve is installed at the center of the pipes which reduces the inner section of the lifting device and does not allow balancing its position in the seating nipple during operation. This generates a high probability of valve blowout at high pressure drops and valve clogging with mechanical impurities during well stopping which hinders valve removal from the nipple. Furthermore, the bellows stem is connected with the gate which increases the probability of breaking the link between the stem and the gate at dynamic loads and hence depressurization of the gate/saddle pair.

Patent search has not revealed any information source disclosing an independent device for fluid flow adjustment in horizontal wells.

The object of this invention is the autonomous adjustment of completion to the fluid inflow due to the specific design features of the device provided herein. It is suggested to achieve said objective by using the autonomous device for fluid flow adjustment in horizontal wells provided herein. Said device comprises an input and an output openings for fluid passage between which there is at least one sequential adjustment stage consisting of sequential or parallel installed hydraulic impedance and valve and/or an insulating (cutoff) element comprising a valve or a series of parallel installed valves that are not capable of automatically opening upon a decrease in the flow of the fluid, and furthermore said device comprises an outer enclosure in which said device components, or at least their part, are contained.

The autonomous fluid flow adjustment device operates as follows. During equipment installing into the well all the valves are open. The liquid and/or gas flow passes through the input device and the open valves and is delivered to the production pipe.

When the flow rate through the valve becomes greater than a certain (preset) value, the valve closes. The fluid flow duct changes, and the flow in the adjustment stage is redirected to flow through an additional hydraulic impedance and the open valve of the next adjustment element. The overall hydraulic impedance of the device increases and the flow drops. If the flow increases again, the next valve in the other adjustment element closes and the flow will return to the hydraulic impedance, etc..

When the flow rate of the fluid reduces (to below the preset value) the gate of the valve of the adjustment element returns to the initial open position thus changing the liquid flow duct and a decrease in the overall hydraulic impedance of the device. The fluid flow rate increases again. If the flow rate decreases again, the next valve in the other adjustment element opens and the flow will bypass the hydraulic impedance of the adjustment element thus increasing the overall flow rate through the device, etc..

Thus, liquid flow rate through the autonomous flow adjustment device will be kept within the preset range regardless of inflow rate.

Furthermore, the cutoff element provides for autonomous (upon exceeding the preset flow rate) or forced isolation of certain well intervals with high gas and/or water inflow. Forced isolation of any well zone can be achieved by selectively increasing the drawdown pressure on the formation causing an increase in the flow rate of the fluid, or using another method depending on the physical principle of valve gate retaining. This design excludes uncontrolled opening of the cutoff element without delivering external pressure or liquid flow rate.

In some embodiments of the device provided herein the adjustment element may comprise a normally open valve and a throttle as hydraulic impedance that can be interconnected either in sequence or in parallel. Actually, these two options are equivalent, and the choice of the option depends on suitability to the well completion equipment used. As compared with sequence connection, parallel connection yet provides for some simpler and hence cheaper design while maintaining the claimed functionality. In different embodiments of the device provided herein, depending on the well completion equipment used, the throttle may be, among others, any known flow diverting and/or reverting, merging and/or splitting, narrowing and/or broadening devices as well as combinations thereof. The choice of a specific hydraulic impedance type depends on the expected operation conditions of the device.

In some embodiments of the device provided herein the adjustment stage may comprise a normally open valve and a nozzle as hydraulic impedance that can be interconnected either in sequence or in parallel. The valve and nozzle connection type depends on the well completion equipment used.

For example, the nozzle can be a device for increasing flow speed in an opening (nozzle, pipe etc.).

The cutoff element may comprise one or more parallel installed valves with a fixed open or closed gate position. This reduces the risk of valve clogging and increases the device cutoff or opening flow rate.

The gate of the valve in the adjustment and/or cutoff element can be made capable of being in open or closed position due to the action of the liquid and/or gas flow, magnetic or electromagnetic fields or an elastic element. The choice of the valve gate position depends on the expected operation conditions of the device.

In some embodiments of the device provided herein, depending on device operation conditions, the gate of at least one of the valves in the adjustment and/or cutoff element can be made capable of switching due to the action of the liquid and/or gas flow, magnetic or electromagnetic fields or an elastic element. The choice of the valve design depends on its expected operation conditions.

The gate of at least one of the valves in the adjustment and/or cutoff element can be completely made from a magnetic material. This allows using magnetic or electromagnetic fields for controlling the valve.

In some embodiments of the device provided herein at least one of the valves in the adjustment and/or cutoff element may comprise setup means for gate retaining and switching. This allows changing device settings if the parameters of the near wellbore formation zone change in time.

In some embodiments of the device provided herein the hydraulic impedance in the adjustment element may also comprise impedance setting means to allow changing device settings during system setting before installing into the well and/or in case of changes in the parameters of the near wellbore formation zone and/or in the well rate.

The device enclosure can be made capable of containing at least one adjustment and/or cutoff element and being connected to the input and output devices. This reduces the size of the enclosure (and hence simplifies the problem of its space requirements) by isolating only part of the device.

In some embodiments of the device provided herein the enclosure may further have one or more pluggable openings for checking and changing device parameters which may be required for checking its leak proofhess, functioning and quality control at the manufacturing stage and, where necessary, changing device parameters before installing into the well.

In different embodiments of the device provided herein the interconnections between the input device, the adjustment element, the cutoff element and the output device can be provided using either similar or different methods.

In different embodiments of the device provided herein the adjustment and cutoff elements can be shifted relative to each other along the device axis. This avoids direct flows and hence dynamic impact upon the valve gate.

In its different embodiments, the device provided herein may comprise either adjustable hydraulic impedance with hydraulic impedance adjustment means or an adjustable valve with valve adjustment means. This allows changing device settings during system setting before lowering into the well and/or in case of changes in the parameters of the near wellbore formation zone and/or in the well rate.

One of the most important advantages of the independent flow adjustment device is the guaranteed and known position of the device. The opening of all the valves can be provided, for example, by increasing wellbore pressure. Then one can reset the entire well completion system to suit the new inflow conditions. It is also possible to close any well zone using any of the abovementioned methods. The autonomous flow adjustment device provided herein can be used for solving a wide range of field development tasks, e.g. achieving uniform inflow rate in horizontal wells, solving the problem of coning in the near wellbore zone, limiting the inflow from super reservoirs or high permeability or cracking zones, limiting water inflow and reducing gas and/or water flow rate from outburst zones. The system can be used for well completion in sandstone or carbonaceous fields.

The use of the device provided herein allows automating the adjustment of fluid inflow in horizontal wells due to the specific design features of the device.