Annular pressure reduction system for horizontal directional drilling

Working an underground arcuate path around at least a portion of an obstacle with a casing extending into the underground arcuate path, connecting a rotating control device to the casing; and a Venturi device connected to the rotating control device.

TECHNICAL FIELD

Horizontal Directional Drilling (referred to as “HDD” below) is a sophisticated technique used to install utilities, such as natural gas pipe lines, electric and many other infrastructural needs under ground level. This technique is steadily becoming more popular in the underground construction industry, in most cases the HDD method has proven over time to be the most cost effective solution in allowing normal every day operations to continue in the construction area surroundings.

BACKGROUND

Drilling mud is a primary ingredient needed in performing HDD crossings, compiled of manufactured clays mined from the earth. Mud properties are responsible for many stages of a successful HDD project. These responsibilities range from steering the down hole tooling, to cooling the tooling, even powering down hole equipment. A vital characteristic of mud used during the drilling process is its ability to carry spoils to surface making clearance for the drilling equipment advancing forward with pipe and tooling underground to varying depths and distances.

Mud operation in a HDD project can be considered a closed circuit configuration. Mud is pumped down hole through the drill string where it exits through various orifices in the down hole drill tooling. It then returns to surface carrying soils and/or cuttings. Once on surface the cuttings saturated mud is pumped to a recycling system where the cuttings are separated from the drilling mud and the clean mud is sent back to the mud pump for reuse.

Horizontal drilling productivity and efficiency is directly related to maintaining constant and continuous drilling fluid or mud “returns” along the bored path back to the entry point at the surface. An event commonly referred to as a “frac-out”, also known as an inadvertent return, occurs when excessive drilling pressure results in drilling mud escaping from the borehole and propagating toward the surface (e.g. the ground fractures and fluid escapes or propagates toward the surface). A frac-out can be costly due to work stoppage for cleanup, can cause safety concerns, and can severely affect environmentally sensitive areas.

A need therefore exists for apparatuses and methods for eliminating or substantially reducing these all too frequent frac-outs or inadvertent returns.

SUMMARY

Working an underground arcuate path around at least a portion of an obstacle with a casing extending into the underground arcuate path, connecting a rotating control device to the casing; and a Venturi device connected to the rotating control device.

As used herein the phrase “rotating control device” is inclusive of rotating blowout preventers or RBOPs, rotating control heads, and other devices to enclose or close an underground arcuate path, to seal to drill pipe (the drill pipe to be optionally turned and axially moved), and to control annular pressure within the space encircling the drill pipe.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details.

With reference toFIG. 1, an exemplary embodiment of a mud recovery system or apparatus10using a rotating control device1, such as a blowout preventer (“RBOP”)2, and venturi device3is depicted. An aspirator/ejector4may be connected to the venturi device3. A horizontal drilling rig or drill rig16loads and advances drill pipe44by turning and pushing into ground or rock formation or earth50at a planned degree of angle through a casing42at entry or entrance A. The casing42adjoins the ground, rock formation or earth50. An RBOP2is used to close, seal or cap the casing, while still allowing rotation of the drill pipe. A mud pump or drill pump22sends drill mud at a calculated pressure and flow through the mud line6towards the drill rig16. Mud then travels through the interior of the drill pipe44exiting the down hole tooling such as a drill bit48(not shown inFIG. 1).

When mud has exited the down hole tooling (not shown inFIG. 1) at high velocity and drill pipe44continues to advance, the surrounding formation50is broken down suspending itself in the drilling mud. The flow continues to travel to the area between the exterior of the drill pipe44and the interior of the bore56(shown inFIG. 3) upward to surface carrying the soils and/or cuttings within the drill mud. The Venturi device3is connected to the rotating control device1, and a venturi mud line pump24pumps through the venturi mud line or venturi flow line14.

Frac-outs or inadvertent returns occur when the annular pressure limits is/are exceeded (relative to the surroundings). When the annular pressure is exceeded, the muds or fluids will follow a less resistant, unintended path often to surface or along a natural path to some other unintended location. In order to reduce the annular pressure, and thus eliminate or mitigate the chances of a frac-out, the mud recovery system10uses an RBOP2and a Venturi device3to take advantage of Bernoulli's principle in pulling, lifting, or sucking or pumping out the muds traveling upward to the surface through the area between the exterior of the drill pipe44and the interior of the bore hole56(shown inFIG. 3) at entry A (also shown inFIG. 3).

The trash pump or dirty mud line pump26pumps dirty mud from the pit18through the dirty mud line8to the mud cleaning unit30. The mud cleaning unit30may be a continuous cleaning system which may utilize a plurality of screens or filters and may include a plurality of centrifuges which clean or separate soils and/or cuttings from the mud. The cleaned mud leaves the mud cleaning unit30through the clean mud line12to the pumping unit20. The mud pump22pumps the muds through the mud line6downhole. The pumping unit20may include the mud pump22and the venturi mud line pump24, or the mud pump22and the venturi mud line pump24may be separate units.

Referring toFIG. 2, a top view of an exemplary embodiment of a mud recovery system or apparatus10using a RBOP2and Venturi device3is shown. The mud recovery system or apparatus10comprises and/or contains, but is not limited to, an apparatus for working an underground arcuate path or horizontal directional drilling path40(shown inFIG. 3) around at least a portion of an obstacle51, such as, by way of example only, a body of water, highway, railroad track, etc. (shown inFIG. 3) comprising a casing42extending into at least a lead portion41of the underground arcuate path40(shown inFIG. 3), a rotating control device1, such as an RBOP2, connected to the casing42, and a venturi device3connected to said rotating control device1. The figure shows the venturi mud line pump24connected to the venturi mudline or venturi flow line14. The trash pump or dirty mud line pump26pumps mud from the pit or entry pit18through the dirty mud line8. The trash pump or dirty mud line pump26, the venturi mud line pump24, and the mud pump or drill pump22(shown inFIG. 1) can be commercially available from a suitable supplier and may be separate or combined. A diffuser (28), such as a steel diffuser, may be connected to the venturi device3. The Venturi device3may be connected to a lateral port5for said rotating control device1at a position external to the drill pipe.

UsingFIGS. 1 and/or 2as a reference, but not limited to the exemplary embodiments depicted inFIGS. 1 and/or 2, the following describes a method for working an underground arcuate path40around an obstacle51(shown inFIG. 3), comprising the steps of: lowering an annular pressure within a space encircling a drill pipe; wherein said step of lowering the annular pressure within the space encircling the drill pipe is performed by sucking a volume of drilling fluid out of the space encircling the drill pipe.

UsingFIGS. 1 and/or 2as a reference, but not limited to the exemplary embodiments depicted inFIGS. 1 and/or 2, the figures depict an apparatus for working an underground arcuate path40(shown inFIG. 3) around at least a portion of an obstacle51(shown inFIG. 3) comprising a casing42extending into at least a lead portion41of the underground arcuate path40(shown inFIG. 3), a rotating control device1, such as an RBOP2, connected to the casing42, and a Venturi device3connected to said rotating control device1.

Referring toFIG. 3, a schematic elevation view of an exemplary embodiment horizontal directional drilling path or underground arcuate path40is shown. There is an entrance or entry A of the arcuate path40and a planned exit point B along the ground or rock formation50, and which the arcuate path40may be worked around at least a portion of an obstacle51. The schematic shows a casing42with the drill pipe44connected to downhole tooling or drill bit48located a height h from the surface of the ground or rock formation50as the drill bit48creates a bore56. The pressure, P1, at point52, also known as the space encircling52the drill pipe44, of the bore, is lower as compared to the pressure, P2, at point54, also known as the space encircling54the drill pipe44, when the drill bit48has progressed to a deeper height further down the path40. The system and/or apparatus and/or method for working an underground arcuate path around at least a portion of an obstacle as disclosed allows for a lower P1and P2, which eliminates or mitigates chances of a frac-outs by reducing the annular pressure such that the pressure the soil or ground or rock formation or earth50can withstand is not exceeded.

While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible.