Injection-point flow control of undamaged polymer

Abstract

A device that allows gradually regulation, i.e., non-destructively controlling the flow of injected polymer flooding enhanced oil recovery fluids at each point of injection, using: at least one conduit providing a variable length flow path combined with the centrifugal and other retarding or decelerative forces accessible to a formation engineer by configuring and otherwise arranging the spatial orientation and relative position of each section of such conduit, so as to achieve a never before attained degree of non-damaging flow control density within a compact space.

Description

BACKGROUND[0001]1. Field of the Invention[0002]This application relates generally to controlling a flow of a polymer fluid injected for the purpose of enhancing oil recovery, and in particular to an apparatus and methods for doing so that delivers a sufficient quantity and quality of polymer fluid (including any gelled form thereof) without “shearing” or other degradation thereof.[0003]2. Description of the Related Art[0004]Traditional oil production methods result in only 20% to 30% of the original oil in place (OOIP) produced up the well hole. Polymer flooding, according to which a viscous body or “plug” of polymer sweeps oil through a formation in a desired direction, is one Enhanced Oil Recovery (“EOR”) technique allowing producers to recover an additional 15% to 20% of the OOIP. The conventional polymer flooding system consists of a source of polymer that is pumped under pressure to at least one injection well (or “point”) adjacent a production well toward which such plugs of f...

AI Technical Summary

Benefits of technology

[0009]Embodiments of the present invention may, for example, include a device for non-destructively controlling the flow of polymer flooding EOR fluids at each point of injection at a well-site using a conduit providing a variable length flow path combined with the centrifugal and other retarding or decelerative forces accessible to a formation engineer by configuring and otherwise arranging the spatial orientation and relative position of each section of such conduit, so as to achieve a never before attained degree of non-damaging flow control density within a compact space.

[0010]Advantageously, such may provide for synchronized multi-point flow control over a polymer flood so as to coordinate multiple polymer wave fronts from different directions to arrive in a timely manner acting on a common production point, thereby implementing a site flooding plan in an efficient manner to make the optimal use of polymer possible. Further, such may allow use of a compact apparatus which employs tightly configured seamless conduit and smoothly joined elements that avoid inducing turbulence despite the continuous deceleration caused by passing the polymer fluid through coils of pipework densely assembled in close proximity and using carefully matched internally machined fittings wherever required.

[0011]According to one aspect, an apparatus may enable a formation engineer to relatively finely tune the flow of polymer fluid required to an injection point sweeping oil towards a defined production well, and then permit a relatively less experienced operator to implement a substantially optimal injection plan, based on installing and operating one such apparatus per injection point. Such may advantageously allow the formation engineer and operators of an injection well-site to refine and / or customize the flow pattern of the site so as to supply a sufficient volume of polymer fluid to each high resistance injection point while simultaneously limiting the volume of polymer flowing into each low resistance injection point, without introducing harmful turbulence at any injection point. When the polymer fluid is delivered to all injection points without degradation, the polymer fluid is better able to sweep oil through the reservoir. If appropriate volumes of polymer fluid synchronously travel through their respective flow controllers and then their respective portions of the formation so as to arrive at their designated locations in a timely manner. The combined sweeping effect of the compressive plugs of polymer fluid may move the oil through the reservoir toward a common production point in a more efficient (i.e., no fingering or breakthrough) fashion than otherwise possible. With the many factors that a formation engineer must accommodate and control in order to optimize production at each injection site, it may be advantageous to install the apparatus at each injection point to provide individually adjustable means for controlling flow without introducing turbulence. The apparatus may permit operators to control the volume of laminar flow of polymer fluid to a particular injection point by varying the effective length and spatial orientation of the drag inducing conduit through which the polymer fluid is required to pass for delivery to that injection point. Much like the “cars” on a roller coaster, the stream of activated polymer fluid moving inside a conduit is subjected not only to the frictional drag between the “wheels and tracks”, corresponding to the tendency for a viscous fluid to adhere to the inner walls of the conduit, but also to the decelerative forces that absorb energy from the stream of polymer fluid as the stream changes direction passing around each curve. Such may be particularly enhanced by use of a helical structure formed by the tubular coils. By this novel means of using the combination of friction and decelerating coils or other loops to restrict the flow of EOR flooding polymer fluid—excess energy is gradually dissipated to avoid turbulence such that the attachment points of the polymer molecules are not exposed to sudden change and thereby sheared. Advantageously, the low resistance injection points are supplied by longer and / or more frequent and tightly looped paths of fluid delivery conduit that delay the arrival of the required volume of polymer fluid into the formation so as to permit an operator to better coordinate delivery with slower moving polymer traveling through high resistance points.

[0012]Accordingly, there may be provided a compact device for reliably adjusting and controlling flow rate at the point of injection by allowing the operator to introduce or omit different series of coils of differing lengths simply by turning any one or all of the bypass valves in the fluid circuit. Not only does such an apparatus permit operators to accommodate the fluid flow factors of: viscosity, density, velocity, active conduit length, inner diameter of available conduit, internal roughness of conduit, transient changes in temperature, and the relative position of supply and discharge manifolds and lines, but it also takes into account and makes use of the centrifugal forces and other naturally decelerative effects of the combinations of possible spatial orientation that are available to the creative engineer within the efficiently limited volume of space. Thus the apparatus may accordingly be constructed, transported, and housed less expensively than otherwise possible.

[0014]According to at least one aspect, there is further provided a method of manufacturing such an apparatus incorporating the use of joint-less welded tubes to prevent deadly leaks of sour water. The present method of manufacturing and the present apparatus may further include a heater that protects aqueous polymer against freezing, and a housing that facilitates leak detection and protection against mechanical damage during transportation and operation.

Problems solved by technology

As explained in more detail below, the objective of sweeping oil toward a production well is complicated by the need to simultaneously control the velocity and volume of multiple wave fronts, flowing from different directions, and ostensibly through zones having different characteristics.

To further complicate matters, when EOR polymers are mixed, static shear mixers hydrate or activate the polymer.

A number of problems result if the composition and flow of the sweeping polymer is not carefully controlled, and each restriction risks damage to the already activated polymer due to abrupt changes in energy level during the transition from high to lower pressure.

However, re-exposing emulsion polymer to such high energy after the polymer is already fully hydrated or activated can damage the large molecules by “shearing” their attachment points that bond the water or carrier molecules.

The flooding performance of a plug of polymer fluid depends on maintaining the bonds formed during activation, so the polymer's utility can be severely limited when overexposed to anything such as restrictions or impellers that can apply excessive mixing energy.

Since the traditional flow controlling restriction is implemented using an orifice such as a choke, turbulence is introduced that causes shear and damages the polymer.

Turbulence involves the collision of molecules such that bonding points are re-exposed and may be damaged.

Consequently, traditional flow control devices such as chokes tend to breakdown the polymer fluid—reducing its viscosity below a useful level.

Whereas at a given injection point the resistance to flow may be very low and another point (within the same field) resistance very high, from a production perspective it would be ineffective to apply the same pressure of polymer fluid supply to both injection points because the fluid will follow the path of least resistance such that the low resistance injection point will consume the majority of the polymer resources leaving less to inject at the high resistance injection point.

The traditional means of restricting flow to the low resistance injection point is to “choke” off the flow of polymer at the injection point, however that results in a sudden change that causes turbulence that is harmful to the polymer.

This method purports to address the problem of shear being induced by individual control over a common polymer source, but disadvantageously relies on a number of expensive hydraulic drivers and pumps to maintain the unique rate of injection required at injection point receiving fluid from a fluctuating common master branch.

These recent systems appear to rely on the long known but inadequately applied principle of drag induced by the relative motion of a viscose fluid inside a conduit.

Disadvantageously, the linear array or cage of pipes comprising even this most relevant of the known prior attempts is bulky and inefficient making use of simple lengths of pipe threaded together, which are not suitable for sour water leak exposure applications.

Within the large physical space required (resulting in a “low density” of flow control) to operate these rudimentary devices the amount of drag that may be induced using their linear form of flow controller is limited to that achieved by taking into account the Reynolds Number of the flow and the internal roughness of the selected pipe together with that resulting from mismatched fittings (both couplings and valves)—that collectively create the risk (above a characteristically relatively low flow rate) of the creation of polymer damaging turbulence such that the volume of flow through their conduit is limited, thereby in turn limiting the maximum flow to at least some of the injection points.

All such restrictions of flow lead to a “weakest link” problem being imposed on the injection plan that the formation engineer would prefer to implement, such that the pace of combined sweep of the polymer wave fronts is also reduced thereby directly reducing the potential production rate of the entire injection site, because the available polymer and injection resources are applied in a less than optimal manner.

Images