US-12624602-B2 - Method for determining a flow rate of a drilling mud in a subsoil drilling system

US12624602B2US 12624602 B2US12624602 B2US 12624602B2US-12624602-B2

Abstract

Method for determining a flow rate of a drilling mud in a subsoil drilling system which includes a main duct and a bypass conduit. The bypass conduit has a narrowed section. The method includes: feeding the bypass conduit with drilling mud, coming from a drilling well formed by the system and carrying drilling cuttings; coupling, to the narrowed section, a differential pressure sensor generating a first signal representative of a difference between a first pressure detected upstream or downstream of the narrowed section and a second pressure detected in the narrowed section; coupling, to the bypass conduit, a thermal dispersion sensor generating a second signal representative of a velocity of the mud; selecting, as a mud flow rate value, one of a first value calculated based on the first signal and on a density value of the mud, and a second value based on the second signal.

Inventors

Antonio Calleri

Assignees

GEOLOG S.R.L.

Dates

Publication Date: 20260512
Application Date: 20230518
Priority Date: 20220519

Claims (15)

1 . A method for determining a flow rate of a drilling mud in a subsoil drilling system, wherein said system comprises a main duct and a bypass conduit having an inlet and an outlet connected to said main duct, said bypass conduit having a narrowed section between said inlet and said outlet, said method comprising: feeding said main duct with drilling mud coming from a drilling well formed by said system, wherein said mud carries cuttings generated by said system while drilling the subsoil, so that at least part of said drilling mud flows into said bypass conduit; coupling a first measurement device with said narrowed section, the first measurement device being a differential pressure sensor configured for generating a first measurement signal representative of a difference between a first pressure detected upstream or downstream of said narrowed section and a second pressure detected in said narrowed section; coupling a second measurement device with said bypass conduit, said second measurement device being a thermal dispersion sensor configured for generating a second measurement signal representative of a velocity of the mud; acquiring a density value of said mud; calculating a first value of the mud flow rate in the bypass conduit based on the first measurement signal and on the density value; calculating a second value of the mud flow rate in the bypass conduit based on the second measurement signal; comparing the first and second value of the mud flow rate with one or more comparison values; selecting one of the first and second values of the mud flow rate based on said comparison; generating an electrical output signal indicative of the selected flow rate value.
2 . The method according to claim 1 , wherein said bypass conduit comprises: a first tract that is substantially vertical and extends from said inlet; a second tract that is inclined with respect to the first tract and terminates with said outlet; a connection portion connecting the first tract and the second tract.
3 . The method according to claim 2 , wherein said narrowed section and the first sensor are arranged on said second tract.
4 . The method according to claim 2 , wherein said second measurement device is coupled to said first tract.
5 . The method according to claim 1 , wherein acquiring the density value comprises: coupling a third measurement device with the bypass conduit, the third measurement device being a differential pressure sensor configured to generate a third measurement signal representative of a difference between a third and a fourth pressure; calculating the density value based on said third measurement signal.
6 . The method according to claim 5 , wherein said third pressure and fourth pressure are detected at positions along the bypass conduit having substantially the same cross-section area.
7 . The method according to claim 5 , wherein said third and fourth pressure are detected along said first tract.
8 . The method according to claim 7 , wherein said one or more comparison values comprise a threshold value, said method comprising: comparing the first flow rate value with the threshold value; comparing the second flow rate value with the threshold value; if the first flow rate value is higher than the threshold value, calculating the flow rate of the drilling mud in the bypass conduit based on the first flow rate value, disregarding the second flow rate value; if the second flow rate value is lower than the threshold value, calculating the flow rate of the drilling mud in the bypass conduit based on the second flow rate value, disregarding the first flow rate value.
9 . The method according to claim 1 , wherein said main duct is located upstream of one or more stations configured to separate said mud from said cuttings.
10 . The method according to claim 1 , wherein no stations configured for separating the mud from the cuttings are present between the drilling well and the main duct.
11 . A process for detecting losses and/or kicks in a subsoil drilling system, comprising: carrying out the method according to claim 1 ; making a comparison between the flow rate of the drilling mud in the bypass conduit and one or more reference parameters, said reference parameters being representative of a presence or absence of possible losses and/or kicks; generating a notification signal as a function of said comparison.
12 . The process according to claim 11 , wherein said one or more reference parameters are correlated with a flow rate of drilling mud being fed to said drilling well.
13 . An apparatus for determining a flow rate of a drilling mud in a subsoil drilling system, comprising: a bypass conduit having an inlet and an outlet connectable to a main duct of said drilling system, said bypass conduit having a narrowed section between said inlet and said outlet, wherein said bypass conduit is configured to receive from said main duct drilling mud coming from a drilling well formed by said system, wherein said mud carries cuttings generated by said system while drilling the subsoil; a first measurement device coupled with said narrowed section, the first measurement device being a differential pressure sensor configured for generating a first measurement signal representative of a difference between a first pressure detected in said narrowed section and a second pressure detected upstream or downstream of said narrowed section; a second measurement device coupled to said bypass conduit, said second measurement device being a thermal dispersion sensor configured for generating a second measurement signal representative of a velocity of the mud; a processor, configured for: acquiring a density value of said mud; calculating a first value of the mud flow rate in the bypass conduit based on the first measurement signal and on the density value; calculating a second value of the mud flow rate in the bypass conduit based on the second measurement signal; comparing the first and second value of the mud flow rate with one or more comparison values; selecting one of the first and second values of the mud flow rate based on said comparison; generating an electrical output signal indicative of the selected flow rate value.
14 . The apparatus according to claim 13 , wherein said bypass conduit comprises: a first tract that is substantially vertical and extends from said inlet; a second tract that is inclined with respect to the first tract and terminates with said outlet; a connection portion connecting the first tract and the second tract, wherein a port for removal of cuttings is provided in said connection portion.
15 . A system for detecting losses and/or kicks in a subsoil drilling system, comprising the apparatus of claim 13 , wherein said processor is further configured for: making a comparison between the flow rate of the drilling mud in the bypass conduit and one or more reference parameters, said reference parameters being representative of a presence or absence of possible losses and/or kicks; generating a notification signal as a function of said comparison.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to Italian Application No. 102022000010436, filed May 19, 2022, which is incorporated herein by specific reference. DESCRIPTION Field of the Invention The present invention relates to a method and an apparatus for determining a flow rate of a drilling mud in a subsoil drilling system. The invention also relates to a process and a system for detecting losses and/or kicks in a subsoil drilling system. Background of the Invention When drilling an oil well (for locating and extracting hydrocarbons in the subsoil) or a geothermal well (for locating and exploiting geothermal resources), a fluid called drilling mud is made to circulate within the borehole in order to lubricate and cool the drill bit. The drilling mud, which is taken from a source tank, is pumped into the hollow interior of the drill string and is made to flow back up to the surface within the annular space, called “annulus”, defined between the drill string and the well walls. After having reached the surface, the returning mud flows, typically at atmospheric pressure, along a return tube, also known as “flow line”, at the end of which the solid debris dragged by the mud is separated from the fluidic component by means of a system of vibrating sieves. The fluidic component of the mud is then fed back into the source tank. The purpose of drilling mud circulation is, therefore, not only to lubricate and cool the drill bit, but also to convey to the surface the solid rocky debris, or “cuttings”, and the fluidic products contained therein. An additional function of the drilling mud is to support the already drilled part of the well. Thanks to the hydrostatic pressure exerted by the mud, it is possible to balance the pressure of the fluids contained in the rocky formations during the drilling. It should be noted, in fact, that without such countering action the fluids contained in the rocky formations would flow uncontrollably in the well during the drilling. In particular, in “static” conditions, i.e., when no mud is circulating in the well, the pressure at the bottom of the well, known as “Bottom Hole Pressure” (BHP), equals the hydrostatic pressure, which essentially depends on the height and mean density of the mud column. In “dynamic” conditions, i.e., when mud is circulating in the well, the BHP value depends on the hydrostatic pressure of the mud and also on the load loss caused by the mud flowing back up along the annulus. In normal operating conditions, i.e., when no losses or kicks occur during the drilling, the flow rate of the mud being pumped into the drill string is substantially equal to the flow rate of the mixture of mud and cuttings being conveyed towards the vibrating sieves by the flow line. However, in the mud circuit, and typically in that portion of the well where the subsoil formation is directly exposed to the mud (“open hole”), losses or kicks may occur. Losses typically occur when the drill bit crosses a faulted formation, or when the BHP in static and/or dynamic conditions is such as to overcome the resistance of one or more rocky formations in the open-hole well portion. Kicks occur when the BHP cannot balance the pressure of the fluids contained in the formation, resulting in unexpected and uncontrolled intake of quantities of fluid (e.g., hydrocarbon) in the drilling mud circuit. Therefore, drilling rigs need to be monitored in order to immediately detect the onset of critical situations such as, for example, losses and/or kicks. The Applicant observes that measuring the rate of the mud flow within the respective tubes may provide useful indications as to the onset of losses and/or kicks. Losses, in fact, lead to a lower flow rate reading, provided that the measurement is taken downstream the loss. Conversely, kicks result in a higher flow rate, which, if not identified in time, may in certain drilling conditions become uncontrollable to the point that the very structure of the drilling rig may be damaged. The Applicant has however verified that the instruments currently available for measuring the flow rate of a drilling mud cannot give sufficiently precise results in all possible drilling conditions. In particular, the so-called electromagnetic flowmeters are precise and reliable for water-based muds only. For oil-based muds, on the contrary, they cannot return acceptable readings. Flowmeters based on the Coriolis principle (“Coriolis flowmeters”) operate in a precise and reliable manner with substantially monophasic fluids. In the case of drilling muds (which are natively complex fluids that, in operation, are found mixed with rocky residues and variable gas quantities), and especially when the quantity of gas contained in the mud exceeds certain thresholds, these flowmeters cannot ensure reliable measurements. The Applicant has also observed that, during the drilling operations, the operating conditions in which the system has to work may