EP1144804A1

EP1144804A1 - Method for detecting inflow of fluid in a well while drilling and implementing device

Info

Publication number: EP1144804A1
Application number: EP99961157A
Authority: EP
Inventors: Thierry Botrel
Original assignee: Elf Exploration Production SAS
Current assignee: Elf Exploration Production SAS
Priority date: 1998-12-23
Filing date: 1999-12-23
Publication date: 2001-10-17
Anticipated expiration: 2019-12-23
Also published as: NO20013116D0; US6540021B1; ATE247222T1; NO320180B1; NO20013116L; WO2000039433A1; DE69910438D1; EP1144804B1

Abstract

The invention concerns a method for detecting inflow of fluid in a well while drilling, characterised in that the drilling is carried out using an installation comprising a hollow cylindrical drill string (3) wherein is injected fresh mud, a tubing (5) defining with the drill string (3) an annular space (7) through which the loaded mud rises; it consists in continuously measuring a heat flow; then in continuously calculating on the basis of said quantity the value of a characteristic representing a thermal equilibrium obtained in the absence of a fluid occurrence formation; and in detecting variations in said characteristic, said variations representing a thermal imbalance, resulting from inflow of fluid in the well (1). The invention is particularly applicable in operating oil drilling installations particularly deep at sea.

Description

METHOD FOR DETECTING A VENT OF FORMING FLUID

IN A WELL DURING DRILLING AND DEVICE FOR THE

IMPLEMENTATION OF THIS PROCESS

TECHNICAL AREA

The present invention relates to a method for detecting the arrival of formation fluids in a well during drilling, as well as a device for implementing this method. It finds its application on well drilling installations, notably petroleum on land or at sea.

STATE OF THE PRIOR ART

The arrival of formation fluids and in particular of gaseous hydrocarbons in a well which occur during drilling or operations are phenomena which should be detected as early as possible in order to facilitate their control in order to minimize their consequences such as uncontrolled eruptions that can cause fires, pollution, destabilization or loss of the well.

The need for early detection of inflows has increased with the development of well drilling under increasingly difficult conditions, such as those encountered in high pressure and high temperature well drilling, as well as in well drilling. submarines in very deep water.

Conventionally, a drilling installation comprises a train of hollow cylindrical rods disposed inside a casing, provided at its lower end with a drilling tool and coupled at its upper part to a rotary drive device. For offshore drilling, the installation also includes an extension tube which connects the upper part of the casing to the surface equipment. During drilling, fresh mud stored in tanks is injected inside the drill string by a mud pump.

After passing through the drilling tool, the mud injected inside the drill string is loaded with rock cuttings formed by the action of the drilling tool on the formation, rises in the defined annular space by the drill string on the one hand and the casing extended by the extension tube and the wall of the hole in during drilling on the other hand, then returns to the storage tanks after removal of the cuttings.

A known method for detecting the inflow of fluids into the well being drilled consists in measuring the difference between the flow rate of injected fresh mud and the flow rate of charged mud which rises, then in comparing this difference with a predetermined threshold. Exceeding this threshold signifying an inflow of fluid.

This difference in flow rate is generally determined indirectly from the measurement of the level of the mud in the storage tanks corrected for known additions of fluids to the mud, such as chemicals, and of the variations in volume of mud in the well associated equipment maneuvers. This determination is also affected by the loss of mud in a part of the formation which can mask or delay the variation of the difference between the flow of fresh mud and the flow of charged mud resulting from the arrival of fluids in the well, difference which is the basis of the detection. The accuracy of such a determination is therefore very poor and insufficient to detect efficiently and early, the inflows of fluid into the wells.

In the case of very deep water drilling, this precision is even worse, due to the movements of the floating marine support which supports the drilling installations and due to cyclic variations in the volume of the extension tube due to heaving. of support. This poor precision is all the more troublesome in this case, as the fracturing pressure of the formations at the fragile point of the well, decreases the maximum admissible volume of a fluid coming without risk of loss of the well. Another method of detecting an inflow of formation fluid is described in document US Pat. No. 4,733,232 of March 22, 1982. It consists in modulating the flow of drilling mud near the bottom of the well and in comparing the pressure pulses which are reflected both in the drill string and in the annular space. The ratio of the reflected pulses being modified by a gas coming which changes the density of the mud which goes up in the annular space, this modification is detected by a computer and used as alarm signal.

Another method of detecting an inflow of formation fluid is described in document EP 621 397 of 25.06.1991. It consists of analyzing the vibrations emitted in the mud at the entrance to the drill string and the vibrations captured at the top of the annular space. These latter vibrations resulting from the propagation, inside the drill string and into the annular space, of the vibrations emitted, are affected by the variations in the characteristics of the mud which change with the arrival of formation fluids in the well. The comparison to by means of an analyzer of the emitted vibrations and the captured vibrations makes it possible to detect the arrival of formation fluids.

These last two methods are sensitive to the cuttings entrained by the mud which goes up in the annular space and can in certain cases be inoperative because of the importance of the reflections of vibrations on the particles of formation rocks which constitute the cuttings.

In addition, their implementation requires the use of expensive equipment.

STATEMENT OF THE INVENTION

The object of the present invention is precisely to remedy these drawbacks and in particular to provide a method and a device for early detection of a formation fluid coming into a well during drilling.

This method and this device can be used for the detection of inflows of fluids in the form of liquid or gaseous hydrocarbons, or of water, during drilling on land or at sea, this detection making it possible to take measures to stop the development of these occurrences or minimize their effects. To this end, the present invention provides a method of detecting an inflow of formation fluid into a well being drilled, said drilling consisting in making a hole in a formation, by means of an installation comprising a drill string hollow cylindrical, disposed inside a casing and into which fresh mud is injected, said drill string, said casing and the wall of the hole in progress defining an annular space through which the charged mud rises, which process is characterized in that it consists:

- to continuously measure the heat flow circulating between the fresh mud and the loaded mud through the wall of the drill string, at a given depth,

- to calculate continuously from said heat flow, the value of a characteristic representative of a thermal equilibrium being established in the absence of an inflow of formation fluid, between the fresh mud circulating inside the train rods and the loaded mud going up in the annular space, and

- Detecting variations above a threshold, of the value of said characteristic, said variations reflecting a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well.

According to another characteristic of the invention, the characteristic representative of the thermal equilibrium is the speed of variation of the heat flux circulating between the fresh mud and the mud loaded through the wall of the drill string, at a given depth. According to another characteristic of the invention, the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the heat flux circulating between the fresh mud and the mud charged through the wall of the train stems, at a given depth.

The drilling installation being carried out from a monitoring and control system, according to another characteristic, the present invention proposes a method which also consists, in the event of detection of a variation of the characteristic, greater than a threshold, to transmit to said system a signal indicative of said detection so that it generates an alarm.

The present invention also relates to a device for detecting the arrival of a formation fluid in a well during drilling, said drilling consisting in making a hole in a formation by means of an installation comprising a drill string hollow cylindrical, placed inside a casing and into which fresh mud is injected, said drill string, said casing and the wall of the hole in progress defining an annular space through which the charged mud rises, which device is characterized in that it comprises: at least one sensor for measuring the heat flow circulating between the fresh mud and the mud loaded through the wall of the drill string, at a given depth, sensor which provides a signal measurement of said thermal flux on an output, calculation means, connected to the output of said sensor, to calculate from measured thermal flux, the value of a characteristic representative of an equilibrium t hermetic being established in the absence of an inflow of formation fluid, between the fresh mud circulating inside the drill string and the charged mud rising in the annular space, and treatment means, connected to a output of the calculation means, for:. detecting variations in the value of said characteristic, greater than a threshold, said variations reflecting a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well, and

. deliver a signal indicative of a fluid coming to an outlet. According to another characteristic of the device of the invention, the characteristic representative of the thermal equilibrium is the speed of variation of the heat flow circulating between the fresh mud and the mud loaded through the wall of the drill string, at a given depth .

According to another characteristic of the device of the invention, the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the thermal flux. flowing between the fresh mud and the loaded mud through the wall of the drill string, at a given depth.

According to another characteristic of the device of the invention, the drilling installation being conducted from a command and control system, said device comprises transmission means connected to the output of the processing means, for transmitting to said system signal indicative of a fluid arrival, so that said system generates an alarm.

The present invention also relates to a second method for detecting an inflow of formation fluid in an underwater well during drilling, said drilling being carried out by means of an installation comprising a train of hollow cylindrical rods, arranged inside a casing extended by an extension tube extending into the water between the seabed and the surface, fresh mud being injected into said drill string which forms with said casing and said extension tube an annular space through which the charged mud rises, which process is characterized in that it consists:

- to continuously measure the heat flux circulating between the charged sludge and the sea water through the wall of the extension tube, at a given depth,

- to calculate continuously from the measured thermal flux, the value of a characteristic representative of a thermal equilibrium being established in the absence of an inflow of formation fluid, between seawater and the charged mud going up in the annular space, and

According to another characteristic of the second method of the invention, the characteristic representative of the thermal equilibrium is the speed of variation of the heat flow circulating between the charged mud and the sea water through the wall of the extension tube, at a given depth. According to another characteristic of the second method of the invention, the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the thermal flux circulating between the charged mud and the sea water through the wall of the extension tube, at a given depth. The subject of the invention is also a second device for detecting the arrival of a formation fluid in an underwater well during drilling, said drilling being carried out by means of an installation comprising a train of hollow cylindrical rods, placed inside a casing extended by an extension tube extending into the water between the bottom and the surface of the sea, mud fresh being injected into said drill string which forms with said casing and said extension tube an annular space through which rises loaded sludge, which device is characterized in that it comprises: at least one sensor for measuring a physical quantity representative of the operation of the well, which provides a signal for measuring a physical quantity on an output, calculation means, connected to the output of the sensor for a physical quantity, for calculating from said physical quantity, the value of a characteristic characteristic of a thermal equilibrium being established in the absence of an inflow of formation fluid, between seawater and the charged mud rising in the annular space, and treatment means, connected to an outlet calculation means, for:. detecting variations in the value of said characteristic, greater than a threshold, said variations reflecting a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well, and

. deliver a signal indicative of a fluid coming to an outlet. According to another characteristic of the second device of the invention, the characteristic representative of the thermal equilibrium is the speed of variation of the measured thermal flux. According to another characteristic of the second device of the invention, the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and the sliding average value of the measured heat flux.

According to another characteristic of the second device of the invention, the drilling installation being conducted from a command and control system, it comprises transmission means connected to the output of the processing means, for transmitting to said system the signal indicative of a fluid arrival, so that said system generates an alarm.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood with the aid of the following description of an embodiment given by way of example, with reference to the appended drawings in which: - Figure 1 schematically represents an installation for drilling an oil well in deep water equipped with a device for detecting the arrival of formation fluid in accordance with the description of the invention.

FIG. 2 is a timing diagram of the essential signals intervening in the device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 represents a submarine oil well 1 being drilled, produced by means of an installation which comprises, a floating platform 2 which supports a train 3 of rods, consisting of cylindrical tubes screwed end to end, provided with its lower end of a drilling tool 4 and at its upper part of an injection head 13. The train 3 of rods is rotated by means not shown in FIG. 1, mounted on the platform 2.

A mud pump 10 sucks fresh mud stored in a tank 8 through a suction pipe 11 and discharges this mud into the injection head 13.

The well being drilled has a casing 5 extended at its upper part by an extension tube 6 and at its lower part by the wall of the hole 5a in progress. The extended casing 5 surrounds the train 3 with rods to form an annular space 7, the upper part of which is connected by a pipe 9 to the tank 8.

The fresh mud discharged by the pump 10 into the injection head 13 is injected inside the train of rods in which it circulates from top to bottom and passes through the drilling tool 4 is loaded with cuttings, then goes up in the annular space 7 and returns via the pipe 9 to the storage tank 8.

The device for detecting the arrival of a formation fluid in the well 1 according to a preferred embodiment of the invention shown in FIG. 1, comprises a sensor 14 for measuring thermal flux mounted against the external wall of the train 3 of rods in the lower part of the annular space 7 to 10 meters above the drilling tool 4.

The sensor 14 delivers on an output 15 a signal representative of the heat flux which flows between the fresh mud and the loaded mud through the internal and external walls of the drill string, at its mounting point. The heat flux measured by the sensor 14 is the quantity of heat exchanged by the charged mud which circulates in the annular space 7, with the fresh mud injected inside the train of rods, via said train of rods. , per unit of time and per unit of surface of the external wall of the train 3 of rods, it is expressed for example in Watt per cm2.

The loaded mud which rises in the annular space 7 having been in contact with the drilled formation, has a temperature different from that of the fresh mud which descends inside the train 3 of rods. Due to this temperature difference, a heat flux circulates between the two sludges, radially through the drill string.

When the drilling conditions, in particular the flow rate, the composition, the temperature of the injected sludge, the pressure drops in the sludge circuit do not vary, a thermal equilibrium is established in the absence of fluid coming into the well. This thermal equilibrium results in particular in a substantially constant difference, between the temperature of the fresh mud which circulates inside the drill string and the temperature of the loaded mud. The measured heat flux, which results from this temperature difference, is therefore also substantially constant.

A coming of formation fluid, produces the following effects:

a significant variation in the thermal conductivity of the sludge which rises in the annular space, owing to the fact that the sludge and the formation fluid have different thermal conductivities, particularly in the case of gas inflows,

a variation in the flow conditions of the loaded sludge, because the sludge and the formation fluid have different viscosities and densities and in the case of gas coming in due to possible expansion of this gas,

- A variation in the temperature of the mud which rises through the annular space, due to the fact that the formation fluid which mixes with the mud has a temperature different from that of the latter.

These variations result in a rapid modification of the heat exchange conditions between the mud which circulates inside the drill string and the mud which rises in the annular space, which results in a rupture of the thermal equilibrium. established prior to the arrival of the formation fluid.

This rupture causes a variation in the heat flux measured by means of the sensor 14.

The output 15 of the sensor 14 is connected to an input of the means 16 for calculating the speed of variation of the heat flux measured by the sensor 14 which deliver on an output 17 a signal representative of the derivative with respect to the time of the measured heat flux.

The output 17 is connected to an input of the processing means 18 which carry out the following operations:

- compare, after filtration, the signal delivered by the calculation means 16, representative of the derivative with respect to the time of the measured heat flux, with a predetermined negative threshold and,

- if this threshold is exceeded, deliver a signal on an output 19. As indicated above, in the absence of inflows of formation fluid, the thermal flux measured by the sensor 14 is substantially constant, its derivative with respect to time is therefore very low.

When a formation fluid comes into the well, the heat flux measured by the sensor 14 varies and its derivative with respect to time becomes strongly negative and exceeds the value of the predetermined threshold.

The filtering of the signal delivered by the means 16 prior to the comparison is a conventional operation which aims to eliminate non-significant variations in fluid inflows. Likewise, fugitive overshoots of thresholds which are not significant of inflows of formation fluid are not taken into account.

The threshold value is determined on site as a function of the conditions for carrying out the drilling such as the thermal gradient, the nature of the fluids, the depth, the drilling diameter, the flow rate of circulation of the drilling fluid. The signal delivered to the output 19 by the processing means 18 is therefore indicative of an inflow of formation fluid into the well.

The output 19 of the processing means is connected to an input of transmission means comprising a transmitter module 20 placed near the sensor 14 and a receiver module 21 placed at the upper part of the annular space 7. The module 21 delivers on a output 22 an image signal of the signal delivered on output 19 by the processing means 18.

A system 23 for controlling the drilling installation, connected to the output 22 of the receiver module 21, generates an alarm in the form of a message displayed on a driving console to warn of a coming of fluid in the well, an operator of the drilling installation, who will actuate the safety shutters not shown in FIG. 1.

The command and control system 23 can also act on the installation for example by actuating the emergency stop devices to limit the effects of the arrival of fluid which has been detected. A variant of the invention consists in transmitting the signal delivered by the sensor 14, by transmission means suitable for calculation means and processing means installed on the platform.

The sensor 14, the calculation means, the processing means and the transmission means may advantageously be mounted on a sleeve which will be inserted between two tubes of the drill string.

This cuff can simultaneously support a usual system for measuring other parameters during drilling such as pressure, inclination of the well, weight on the tool. A variant of the embodiment of the invention described above consists in mounting two devices for detecting the arrival of formation fluids on the outer wall of the drill string at different depths and in measuring the time interval between detection fluid coming in from each of the two devices.

The interval thus measured gives an indication of the nature of the coming. Indeed, a gas inflow propagating faster than a liquid inflow, the time interval measured in the first case will be shorter than that measured in the second. FIG. 2 represents a timing diagram of the main signals intervening in the device of the invention represented in FIG. 1.

F represents the evolution of the heat flux measured by means of the sensor 14 as a function of time, a coming of fluid in the well appearing at the instant to. dF / dT represents the speed of variation of the heat flux measured as a function of time, S is the value of the predetermined threshold whose exceeding makes it possible to detect an inflow of fluid.

Sg represents the signal delivered by the processing means, indicative of a fluid coming into the well.

Thanks to the invention it is possible to detect early an inflow of formation fluid in a well being drilled in the form of gaseous and / or liquid hydrocarbons, and or water without risk of delay or masking by a loss. of mud in training and at a lower cost.

In addition, in the case of drilling an underwater well, the method and the device of the invention are insensitive to the movements of the platform and to the variations in volume of the extension tube, and in all cases to the presence of cuttings in the loaded mud.

Claims

- Method for detecting an inflow of formation fluid into a well (1) during drilling, said drilling consisting in making a hole (5) in a formation, by means of an installation comprising a train (3) of hollow cylindrical rods, disposed inside a casing (5) and into which is injected fresh mud, said train (3) of rods, said casing (5) and the wall of the hole (5a) being embodiment defining an annular space (7) through which the charged mud rises, which method is characterized in that it consists in: - continuously measuring the heat flow circulating between the fresh mud and the charged mud through the wall of the train (3) of rods, at a given depth, to be calculated continuously from said thermal flux, the value of a characteristic representative of a thermal equilibrium being established in the absence of an inflow of formation fluid, between the fresh mud flowing inside the rod train (3) s and the charged mud rising in the annular space (7), and detecting variations greater than a threshold, of the value of said characteristic, said variations translating a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well (1). - Method according to claim 1, characterized in that the characteristic characteristic of the thermal equilibrium is the speed of variation of the heat flow circulating between the fresh mud and the mud loaded through the wall of the train (3) of rods, a given depth. - Method according to claim 1, characterized in that the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the thermal flux circulating between the fresh mud and the mud charged through the wall of the train (3) of rods, at a given depth. - Method according to any one of claims 1 to 3, characterized in that the drilling installation being conducted from a command and control system, it further consists, in the event of detection of a variation of the characteristic representative of thermal equilibrium above a threshold, to transmit to said system a signal representative of said detection so that it generates an alarm. - Device for detecting the arrival of formation fluid in a well (1) during drilling, said drilling consisting in making a hole (5a) in a formation by means of an installation comprising a train (3) of hollow cylindrical rods, disposed inside a casing (5) and in which is injected with fresh mud, said train (3) of rods, said casing (5) and the wall of the hole (5a) in progress defining an annular space (7) through which the charged mud rises, which device is characterized in that it comprises: - at least one sensor for measuring the heat flow circulating between the fresh mud and the mud loaded through the wall of the train (3) of rods, at a given depth, sensor which provides a signal of measurement of said thermal flux on an output, calculation means, connected to the output of said sensor, for calculating from measured thermal flux, the value of a characteristic representative of a thermal equilibrium being established in the absence of a inflow of formation fluid, between the fresh mud circulating inside the train (3) of rods and the charged mud rising in the annular space (7), and treatment means, connected to an output of the calculation means , to:> detect variations in the v aleur of said characteristic, greater than a threshold, said variations translating a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well (1), and. deliver a signal indicative of a fluid coming to an outlet. - Device according to claim 5 characterized in that the characteristic characteristic of thermal equilibrium is the speed of variation of the heat flow flowing between the fresh mud and the mud loaded through the wall of the drill string, at a given depth. - Device according to claim 5 characterized in that the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the thermal flux circulating between the fresh mud and the mud loaded through the wall of the train of stems, at a given depth. - Device according to any one of claims 5 to 7 characterized in that, the drilling installation being conducted from a command and control system, it comprises transmission means connected to the output of the processing means, for transmitting to the said system the signal indicative of an inflow of fluid, so that the said system generates an alarm. - Method for detecting the arrival of a formation fluid in an underwater well (1) during drilling, said drilling being carried out by means of an installation comprising a train (3) of hollow cylindrical rods, disposed at the interior of a casing (5) extended by an extension tube extending into the water between the seabed and the surface, fresh mud being injected into said train (3) of rods which forms with said casing (5) and said tube extension of an annular space (7) through which the charged mud rises, which method is characterized in that it consists in: continuously measuring the heat flux circulating between the charged mud and the sea water through the wall of the extension tube, at a given depth, to be calculated continuously from the measured heat flux, the value of a characteristic representative of a thermal equilibrium being established in the absence of an inflow of formation fluid, between the seawater and the charged mud rising in the annular space (7), and - detecting variations greater than a threshold, of the value of said characteristic, said variations translating a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well (1). - Method according to claim 9, characterized in that the characteristic characteristic of the thermal equilibrium is the speed of variation of the heat flow circulating between the charged mud and the sea water through the wall of the extension tube, to a depth given. - Method according to claim 9, characterized in that the characteristic representative of the thermal equilibrium is the difference between the instantaneous value and a sliding time average value of the thermal flux flowing between the charged mud and the sea water through the wall of the extension tube, at a given depth. - Method according to any one of claims 9 to 11, characterized in that the drilling installation being conducted from a command and control system, it also consists, in the event of detection of a variation in the characteristic representative of thermal equilibrium above a threshold, to transmit to said system a signal representative of said detection so that it generates an alarm. - Device for detecting the arrival of a formation fluid in an underwater well (1) during drilling, said drilling being carried out by means of an installation comprising a train (3) of hollow cylindrical rods, arranged at inside a casing (5) extended by an extension tube extending into the water between the seabed and the surface, fresh mud being injected into said train (3) of rods which forms with said casing (5) and said extension tube an annular space (7) through which the charged mud rises, which device is characterized in that it comprises: at least one sensor for measuring the heat flux circulating between the charged mud and the sea water through the wall of the extension tube, at a given depth, sensor which provides a measurement signal of said thermal flux on an outlet, calculation means, connected to the output of said sensor, for calculating from the measured thermal flux, the value of a characteristic representative of a thermal equilibrium being established in the absence of an inflow of formation fluid, between the loaded mud rising in the annular space (7) and the sea water through the wall of the extension tube, at a given depth, and treatment means, connected to an outlet of the calculation means, for:. detecting variations in the value of said characteristic, greater than a threshold, said variations reflecting a rupture of said thermal equilibrium resulting from the arrival of formation fluid in the well (1), and. deliver a signal indicative of a fluid coming to an outlet. - Device according to claim 13 characterized in that the characteristic representative of the thermal equilibrium is the speed of variation of the measured thermal flux. - Device according to claim 13 characterized in that the characteristic representative of the thermal balance is the difference between the instantaneous value and the sliding average value of the measured heat flux. - Device according to any one of claims 13 to 15 characterized in that, the drilling installation being conducted from a command and control system, it comprises transmission means connected to the output of the processing means, for transmitting to the said system the signal indicative of an inflow of fluid, so that the said system generates an alarm.