Patent Application
20250146398
The present disclosure generally relates to hydrocarbon production, in particular hydrocarbon production from a multipurpose well.
Waste water production with oil and gas is a challenge for the oil and natural gas industry. During the production of oil and natural gas, the oil and natural gas sometimes also includes water. The water produced through wells can originate from the hydrocarbon bearing zones, from aquifers that are near the hydrocarbon bearing zones, or from water that is injected downhole. Various chemicals are sometimes also mixed with the injection water to improve the reservoir sweep efficiency. When produced at the surface, this mixture of water and at least one of oil or gas can create a concern from an environmental standpoint.
Sources of water can be wells having a completion depth close to the water zone, high permeability paths from the aquifer to the well trajectory, and high reservoir pressure drawdown accelerating the water cones to develop quickly towards the producer's lateral(s).
This specification describes an approach to separating hydrocarbons from water downhole and producing the hydrocarbons to the surface while injecting the water back into the formation. In particular, this approach uses a downhole separation mechanism for water to allow the gas/oil travel up while reinjecting the separated water back to the aquifer through a predesigned downhole path equipped with a water pump. The associated systems and methods can allow the hydrocarbons to flow naturally to the surface or, as may be needed in mature fields, include pumps or compressors to produce the hydrocarbons to the surface.
Implementations of the systems and methods described in this specification can provide one or more of the following advantages.
The downhole separation of water from production fluids and injection of water back into the formation provides significant advantages. The production fluids are often a mixture of gas, oil and water. In the case of an oil well, the operating pressure downhole can be below the bubble point pressure or the well can have gas produced from the gas cap together with the oil. For gas wells, the gas is often produced with condensate and water.
This approach can reduce capital expenditures by using a single well as a producer and disposal/injector without requiring sidetracking. The savings can be significant as some estimates indicate that the sidetracking required by other approaches cost an average of $3,000,000 USD.
It can also reduce operating expenses since the produced water is directly disposed instead of handling at the surface thus avoiding the costs associated with producing water to surface, treating it, and drilling a new well, and disposing of the water.
This approach can also enhance production. For example, downhole fluid separation can lead to recovering dry gas rather than wet gas. In addition, injecting separated water back into the formation below the hydrocarbons being produced can also act as a water injection well helping lift and/or mobilize the hydrocarbons being produced.
The associated systems and methods can also be used in reviving dead wells by addressing low/moderate water cut and high surface back pressure.
The details of one or more embodiments of these systems and methods are set forth in the accompanying drawings and the description to be presented. Other features, objects, and advantages of these systems and methods will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
This specification describes an approach to separating hydrocarbons from water downhole and producing the hydrocarbons to the surface while injecting the water back into the formation. In particular, this approach uses a downhole separation mechanism for water to allow the gas/oil travel up while reinjecting the separated water back to the aquifer through a predesigned downhole path equipped with a water pump. The associated systems and methods can allow the hydrocarbons to flow naturally to the surface or, as may be needed in mature fields, include pumps or compressors to produce the hydrocarbons to the surface.
The system 100 is installed in the casing 120 of the well. The system 100 includes a liquid-gas separator 122, a liquid collection vessel 124, an intelligent valve system 126, separation chambers 127, separated water tubing 128, and a pump 130. The casing 120 and seals 132 (e.g., packers or plugs) extending across the borehole cooperate with the system 100 to define the flowpaths through which fluids flow.
The liquid-gas separator 122 separates a multiphase produced fluid 134 into a liquid-dominated stream 126 (e.g., a stream having a gas volume fraction (GVF)<5%) and a gas-dominated stream 128 (e.g., a stream having a GVF>95%). The liquid-gas separator 122 can implement gravity, shrouds, or cylindrical cyclonic separation techniques.
The gas-dominated stream 128 flows to the surface and the liquid-dominated stream 126 is routed into the liquid collection vessel 124. The liquid collection vessel 124 functions to capture the liquid in preparation to pumping it down into the formation. The intelligent valve system 126 is operated based on water saturation. The valve system opens (e.g., between 98% and 100% water saturation) and the pump 130 is activated to begin injecting water into the water zone 116 of the subsurface formation 112. When the water saturation drops below a specified value (e.g., is less than 95%), the system unloads and lowers the pressure at the bottom of the active reservoir. This allows for better separation and also protects the pump 130 (e.g. from vapor lock).
The separated water tubing 128 extends downhole from the liquid collection vessel through the casing 120 to the water zone 116 of the subsurface formation 112. The portion of the well 10 in which the separated water tubing 128 runs within the casing 120 is sometimes referred to as the “dual tubing” portion of the well 110. Typically, another seal 132 is installed at the bottom of the casing 120 and/or the casing is cemented around the separated water tubing 128. The separated water tubing 128 extends past the bottom seal and/or cement to discharge in the water zone 116.
The pump 130 is installed in the separated water tubing 128. The separated water tubing 128 is typically a non-metallic tubing which provides corrosion resistance], but in some implementations is a metallic pipe. The pump 130 is typically an inverted electrical submersible pump, but in some implementations is a regular downhole pump.
Although discussed in the context of separating water and gas, a similar approach can be used to separate produced water from oil. In implementations for this application, the liquid-gas separator of the system 100 is replaced by an oil-water separator. Some implementations includes a liquid-gas separation system in series with an oil-water separation system for a field in which the produced fluids contained water, oil, and gas?
The system 100 is illustrated with the gas flowing naturally to the surface without artificial lift systems. However, implementations in mature fields may include compressors (e.g., for gas fields) or pumps (e.g., for oilfields) to produce the hydrocarbons to the surface.
The well will then be drilled to the touchdown of the water tubing (step 312) following the recommended drilling practices for the selected location. The wellbore will be cased, the water tubing be installed, and the well will be cemented around the water tubing (step 314). After cementing, the water pump will be run and set. Typically, a Y-tool will be run in with the water pump to provide access if needed and to perform the setting. The well completion and the liquid-gas separator are then run and set (step 316). They may be set mechanically, hydraulically, or using expandable elements. The isolation packers will then be set before the well is cleaned up and production started (step 318).
During production, operators will monitor gas and water volumes at the surface as well as pressure measurements at the pump (step 320). When an increase in the water cut is observed, the system is activated to separate water from hydrocarbons before inject the water down into formation.
A similar approach can be used to install and operate downhole separation systems in producing and dead wells. In both situations, workover involvement is needed to install the dual tubing completion and place the downhole separator with downhole pump.
In particular, well modifications are designed after a request from the reservoir to install the dual tubing completion and place the downhole separator with downhole pump. A new completion and the dual tubing with pipe collector are run in. If necessary, the old casing is retrieved. The designed path is drilled and cased before steps 316-320 of the method 300 are performed.
The pump 418 is operated by a drive motor (not shown) powered from the surface (e.g., by a power cable). The drive motor rotates a shaft 420 of the pump 418. Although the pump 418 is illustrated in a single stage format for illustration purposes, the blades are typically provided in multiple stages. The pump 418 discharges to a hollow portion 422 of shaft 420 which is connected to the water tubing (not shown). As previously discussed with reference to
In an example implementation, systems and methods for downhole separation of water from hydrocarbons in a wellbore include a first seal limiting flow of fluids downhole in the wellbore and a second seal limiting flow of fluids uphole in the wellbore. A hydrocarbon separator is positioned to receive fluids present in the wellbore between the first seal and the second seal and discharge hydrocarbons into the wellbore uphole of the second seal. A liquid collection vessel receives water discharged by the hydrocarbon separator. A conduit extends downhole from the liquid collection vessel through the first seal and the second seal. A pump installed with the conduit is operable to pump fluids from liquid collection vessel downhole and out of the wellbore.
In an aspect combinable with the example implementation, the hydrocarbon separator includes a liquid-gas separator. In some cases, the hydrocarbon separator further comprises a water-oil separator.
In another aspect combinable with any of the previous aspects, the hydrocarbon separator includes a water-gas separator.
In another aspect combinable with any of the previous aspects, the hydrocarbon separator includes a water-oil separator.
In another aspect combinable with any of the previous aspects, a valve system operated based on water saturation is also included. In some cases, the valve system is configured to open when water saturation in the liquid collection vessel exceeds 98% and/or the valve system is configured to close when water saturation in the liquid collection vessel drops 95%.
In another aspect combinable with any of the previous aspects, a third seal installed at the bottom of the casing is also included. In some cases, the conduit extends past the third seal.
In another aspect combinable with any of the previous aspects, the casing is cemented around the separated water tubing below the second seal.
In another aspect combinable with any of the previous aspects, the pump is an inverted electrical submersible pump.
In another aspect combinable with any of the previous aspects, the first seal and the second seal include packers.
A number of embodiments of these systems and methods have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims.
