Apparatus and Related Methods to Determine Hole Cleaning, Well Bore Stability and Volumetric Cuttings Measurements

A method for estimating a parameter relating to solids recovered from a wellbore may include drilling a wellbore using a bottomhole assembly; conveying solids in the wellbore to a surface location using a drilling fluid; separating the drilling fluid from the solids using at least one shaker; conveying the separated solids by using a conveyor; and continuously dropping the solids into a solids evaluator positioned vertically above the dryer. The solids evaluator includes a chute having a vertically aligned bore in which the dropped solids reach a constant velocity, a sensor assembly generating a microwave field in a section of the chute where the dropped solids have the constant velocity, and a control unit in signal communication with the sensor assembly. The control unit estimates a mass flow rate of the solids based on the generated signals. The method may further include generating the signals representative of a mass flow rate of the dropped solids using the sensor assembly and using the control unit to estimate the mass flow rate of the solids based on the generated signals.

1. FIELD OF THE DISCLOSURE

This disclosure is directed to systems and related methods for estimating one or more subsurface parameters. Such parameters may relate to a drilled borehole, drilling equipment, a formation, and/or fluids in the formation.

2. BACKGROUND OF THE DISCLOSURE

To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to the bottom of a drilling assembly (also referred to herein as a “Bottom Hole Assembly” or (“BHA”). The drilling assembly is attached to the bottom of a tubing, which is usually either a jointed rigid pipe or a relatively flexible spoolable tubing commonly referred to in the art as “coiled tubing.” During drilling, a drilling fluid (also referred to as the “mud”) is supplied under pressure into the tubing. The drilling fluid passes through the drilling assembly and then discharges at the drill bit bottom. The drilling fluid provides lubrication to the drill bit and carries to the surface rock pieces disintegrated by the drill bit in drilling the wellbore. The drilling fluid and entrained materials return to the surface where they are processed.

The present disclosure provides information relating to the borehole by analyzing the materials carried by the drilling fluid to the surface.

SUMMARY OF THE DISCLOSURE

In aspects, the present disclosure provides a method for estimating a parameter relating to solids recovered from a wellbore. The method may include the steps of flowing the solids at a constant velocity through a microwave field, wherein the solids were separated from a drilling fluid recovered from the wellbore; generating signals representative of a mass of the flowing solids; and estimating a mass flow rate using the generated signals.

In aspects, the present disclosure provides a further method for estimating a parameter relating to solids recovered from a wellbore. The method may include drilling a wellbore using a bottomhole assembly; conveying the solids in the wellbore to a surface location using a drilling fluid; separating the drilling fluid from the solids using at least one shaker; conveying substantially all of the separated solids by using a conveyor; continuously dropping the solids into a solids evaluator positioned vertically above the dryer. The solids evaluator may include a chute having a vertically aligned bore, the chute having a length selected to allow the dropped solids to reach a constant velocity, a sensor assembly generating a microwave field in a section of the chute where the dropped solids have the constant velocity, and a control unit in signal communication with the sensor assembly. The control unit may be configured to estimate a mass flow rate of the solids based on the generated signals. The method may further include the steps of generating the signals representative of a mass flow rate of the dropped solids using the sensor assembly; using the control unit to estimate the mass flow rate of the solids based on the generated signals; and drying the solids in a dryer.

In aspects, the present disclosure provides an apparatus for estimating a parameter relating to solids recovered from a wellbore wherein the solids are dropped from a conveyance device. The apparatus may include a chute having a vertically aligned bore, the chute having a length selected to allow the dropped solids to reach a constant velocity, a sensor assembly generating a microwave field in a section of the chute where the dropped solids have the constant velocity, the sensor assembly generating signals representative of a mass flow rate of the dropped solids, and a control unit in signal communication with the sensor assembly, the control unit being configured to estimate a mass flow rate of the solids based on the generated signals.

Examples of certain features of the disclosure have been summarized (albeit rather broadly) in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto.

DETAILED DESCRIPTION OF THE DISCLOSURE

Embodiments of the present disclosure may be used to estimate one or more subsurface parameters by evaluating rock, earth, and other debris carried by drilling fluid to the surface during drilling. Such parameters may relate to a drilled borehole, drilling equipment, a formation, and/or fluids in the formation. The present teachings may be used for land-based drilling or offshore operations. Merely for brevity, an offshore rig will be used as a context to describe illustrative embodiments of the present disclosure.

FIG. 1shows a schematic elevation view of a drilling system10for drilling subsea wellbore12in an earthen formation13. The drilling system10includes a drilling platform14, which may be a drill ship or another suitable surface work station such as a floating platform or a semi-submersible. The subsea wellbore12is drilled by a drill bit of a bottom hole assembly (“BHA”)20carried by a suitable drill string22, such as continuous coiled tubing, drill pipe or other suitable jointed tubulars such as liner or casing. During drilling, a drilling fluid from a surface mud system is pumped under pressure down the tubing22. The drill bit, when rotated, disintegrates the formation (rock) into cuttings. The drilling fluid leaving the drill bit travels uphole through the annulus between the drill string and the wellbore wall carrying the entrained drill cuttings. The returning drilling fluid may also carry particles, such as sand or silt, from the formation and “cavings,” which are rocks and debris that have broken off from a borehole wall. For convenience, all such material will be collectively referred to as “cuttings.” Moreover, “cuttings” and “solids” will be used interchangeably. A return line16, which may be a riser, carries the fluid returning from the wellbore12, along with all such entrained material, to the sea level.

Conventionally, the rig14may include systems for processing the entrained material and drilling fluid. For instance, the rig may include one or more shakers30that separate the drilling fluid from the entrained material and one or more dryers32that clean and dry the separated entrained material.

In embodiments, the rig14may include a solids evaluator40that is configured to analyze the separated entrained material and provide drilling personnel with information that can assist in controlling drilling operations. In some embodiments, personnel may be provided an estimate of the actual quantity of solid material being recovered. Such information may assist evaluating theoretical hole cleaning and/or modeling the stability of the wellbore. Such information may also highlight operational problems such as cuttings bed build-up, show effectiveness of actions (drilling changes, sweeps, mud changes, etc), assist in optimizing operations (e.g., ROP control, mud rheology, surface RPM range, etc), and help minimize unnecessary rig operations (e.g., wiper trips, reaming at connection, non-essential sweeps etc.).

Referring toFIG. 2, there is shown one non-limiting system34for processing drilling fluids and entrained materials. The system34may include one or more shakers30, a conveyor system36, and one or more dryers32. The shakers30capture the cuttings and large solids from the drilling fluid recovered from the wellbore12(FIG. 1). A screen (not shown) is fitted on each shaker of certain mesh size and is vibrated to facilitate separation of the majority of fluids from the solids. The conveyor system36, which include augers, collects the separated solids from all of the shakers30and conveys the solids to the dryer32. The solids free fall from the conveyor system36into the dryer32. In other embodiments, the solids free fall into another conveyor (not shown), a container, or other structure. That is, the solids do not necessarily have to free fall directly into the dryer32. Also, it should be noted that the solids exiting the conveyor36comprise all or substantially all of the solids that have been recovered from the wellbore12(FIG. 1). By substantially, it is meant at least seventy percent or at least enough to furnish information representative of subsurface conditions to an accuracy known to those skilled in the art.

In embodiments, the solids evaluator40may be used to estimate one or more parameters associated with the solids travelling from the conveyor36to the dryer32. In one embodiment, the solids evaluator may include a sensor assembly42and a control system44. In one arrangement, the sensor assembly42uses one or more microwave sensors to generate signals that characterize the separated solids. The sensor signals may be analog and/or digital and transmitted through cables or wirelessly.

The control system44may be in signal communication with the sensor assembly42. The communication can be bi-directional, which may allow the control system44to control the sensor assembly42. The control system44may be positioned on the rig14or located at a remote location, which may be onshore and possibly thousands of miles away. To process the sensor signals, the control system44may include known equipment such as transceivers, microprocessors, memory modules loaded with algorithms, databases, etc. In some arrangements, the sensor information may be received as an estimated mass flow rate, given in tons/hour.

Referring now toFIG. 3, there is shown a solids evaluator40that may be used to estimate one or more parameters associated with the solids travelling from the conveyor36to the dryer32. In one embodiment, the solids evaluator40may include a chute50and a sensor unit60. The chute50may be a thin-walled duct-type structure having a bore51that is vertically aligned. The vertical alignment allows solids to free-fall through the chute50with minimal obstruction. By “free-fall,” it is meant that gravity is the principal force moving the solids and that the solids are moving in primarily a vertical direction. In some embodiments, the chute50may be a barrel-shaped tubular, but in other embodiments may have a non-circular shape (e.g., rectangular shape). Further, the chute50may have a non-varying cross-sectional flow area or a funnel-like shape wherein an inlet52is larger than the outlet54. In embodiments, the chute has a length sufficient to allow the free falling solids in the bore51to reach a constant velocity before reaching the sensor unit60. The chute50positions the sensor unit60above the dryer32(FIG. 2) and orients the sensor unit60such that the microwaves radiate perpendicular to the flow of cuttings56. The sensor unit60may be relatively compact and require minimal space for installation, e.g., roughly about 12 inches. Because microwaves are used, the sensor system60is minimally invasive and has no moving parts.

The sensor unit60may be a microwave-based device that generates an electromagnetic field through which the falling solids passes. In one arrangement, the sensor unit60may include one or more microwave sensors62and a receiver64that are positioned at a location along the bore51where the solids have a constant velocity. The sensor62may be positioned to have an angular offset from a direction of motion of the solids (e.g., ninety degrees) and configured to emit a beam that completely traverses the cross-sectional flow path of the chute50. In embodiments, the microwave field is positioned such as to detect the free falling solids after the solids have reached a constant velocity. As the solids move through the microwave field, the microwaves contacting the solids undergo a Doppler shift, which is then detected by the receiver64. The receiver64is positioned to detect the reflected waves and generate an electrical signal66that is proportional to the concentration of the solids flowing through the chute50. The sensor signal66may be transmitted to the control system44for processing.

In an exemplary use, personnel may first assemble information that may be useful for estimating the desired wellbore characteristics and operating efficiency. Without limitation, this information may include, actual or estimated rate of penetration (ROP), drill bit rotation (RPM), drilling mud properties, drill bit diameter, actual or estimated drilling mud circulation rates, formation lithology, etc. The density of the solids may be determined by testing the recovered solids, testing samples taken from the formation, and/or by using lithology/mineral reference guides. Thus, the density is predetermined, determined before the solids evaluator50is operated. Also, the system44may be calibrated to ensure that the sensor assembly60only measures moving solids as opposed to deposits and/or build ups. For example, the amplitude and frequency of the microwaves can be adjusted in order to obtain an estimate of solids flow within a pre-determined accuracy.

During an exemplary wellbore drilling operation, the BHA20disintegrates the formation and produces cuttings entrained in the circulating drilling fluid. After being separated from the drilling fluid by the shakers30, the cuttings, or solids, the conveyors66continuously drop these solids into the chute50. By continuous, it is meant that the flow of solids is uninterrupted and the downward flow is not halted at an intermediate location prior to entering the dryer32or other structure. Thus, the dropped solids move flow in the aggregate much like a continuous body and are evaluated while in motion. This is in contrast to “batch” operations wherein discrete quantities are periodically dispensed or captured. The sensor assembly60generates a microwave field that completely traverses a cross-sectional flow path of the dropped solids and is perpendicular to the flow of the dropped solids. The sensor assembly60generates an output that may be tons per hour. The control system44converts the sensor output into a volumetric measurement using information such as the estimated density of the material making up the solids.

Once converted, this measurement may be plotted against theoretical hole volume. Through utilization of lag calculations and theoretical volume calculations, personnel may display plots of the theoretical cuttings volume to the actual cuttings volume and the difference (if any) between the two. The differences may provide insight into well conditions. For instance, actual cuttings volumes well below the theoretical cuttings volumes may indicate that hole cleaning is inefficient and is not adequately transporting cuttings to the surface. In contrast, actual cuttings volumes in excess of theoretical cuttings volumes may indicate that portions of the wellbore have collapsed (caving). Another usage may involve estimating a volumetric flow rate using the estimated mass flow rate and an estimated density of the solids and then comparing the estimated volumetric flow rate with a theoretically volumetric flow rate.

Based on the determined differences, a well operator may adjust one or more drilling parameters. A drilling parameter is any condition or operating set-point that can be controlled. Illustrative, but not exhaustive drilling parameters include, ROP, weight on bit (WOB), drill bit revolution, drilling mud circulation rate, drilling mud weight, etc. Thus, it should be appreciated that the information provided by the systems and related methods of the present disclosure may be used to identify hole cleaning efficiency and potential well bore stability issues.

It should be understood that the teachings of the present disclosure are susceptible to numerous variants. For example, the sensor assembly40may be positioned at any location so long as the solids are substantially free of liquids, comprise all or substantially all of the solids recovered from the wellbore, and have a constant velocity. Illustrated inFIG. 4, is one such non-limiting variant of the present disclosure.

InFIG. 4, the solids evaluator40includes a sensor assembly40positioned at each of the shakers30. While three sensor assemblies40are shown, greater or fewer may be used. It is desirable to have a sensor assembly40associated with every shaker30so that all the cuttings retrieved from the wellbore can be evaluated. A rig side control unit44is in signal communication with the sensor assemblies44. The rig side control unit44can provide local personnel with real time or near real time information related to solids flow rates. Additionally, the rig side control unit44can be in signal communication with a remote system70and provide remote personnel with similar information. The remote system70may be on the rig, at another offshore site, or an onshore site.