GB2511143A

GB2511143A - The oil mud weight watcher or MWW

Info

Publication number: GB2511143A
Application number: GB1306464.7A
Authority: GB
Inventors: Ross Lamond Colquhoun
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-02-20
Filing date: 2013-04-10
Publication date: 2014-08-27
Also published as: GB201306464D0; GB201302950D0

Abstract

A device to measure and display the density of any drilling fluid (mud, OBM, WBM) used while drilling for oil or gas at an ambient circulating temperature automatically calculates and displays this density at a fixed and known temperature, known as the referred density. A mud balance is used to measure the mud circulating density (line density) at ambient operating temperatures. The device uses a viscometer and potentiometer 1-3, 1-10, to provide a referred density reading 1-1, which is a density value at a referred or fixed temperature. The device is calibrated to display the correct circulating density reading 1-7 and it automatically recalibrates the referred density value on the display 1-1, using a slave gear 1-4 between the two potentiometers 1-3, 1-10.

Description

This invention relates to a device and system known as The Oil Mud Weight Watcher or The Mud Weight Watcher or the MWW which S allows automatic compensation for the variations caused by temperature on the Density of a Drilling Fluid commonly known as Mud which is used during the process of drilling for Oil and Gas For sate and successful Oil well drilling it is vital that the weight or Density of the Mud is correct for a particular location as its function among other things is to form a hydrostatic column which among other things prevents leakage into the well bore from the formations being drilled and in addition stabilises the well bore and prevents it from collapsing.

Each drilling location and section of the hole being drilled can have different weigh requirements which normally vary for 10.00 ppg (pounds per barrel) to 18.00 ppg although it may be lower or higher than this range.

The temperature of the Mud in circulation varies considerably.

Depending on the location and the stage of the drilling operation, this might range from 5°C to 80°C or some such values although it may be lower or higher than this range.

The different types of Mud commonly used are affected by this variation. Generally as the Mud warms the density falls and as it cools the density increases and with different Muds types being affected differently.

There are two main types of Mud used while drilling 1 Water Based Mud also known as WBM 2 Oil Based Mud also as known as 0DM.

Although both types of Mud are affected by temperature variations,, the inventor has found that OBMs are much more affected than WBMs so this invention relates primarily but not exclusively to OBMs.

OEM is generally an emulsion of three so called phases 1 Oil 2 Water or Brine 3 solids The inventor has found that although all three components are affected by temperature and expand when heated and contract when cooled the effect on the so called Oil phase is much greater than the other phases.

The variation of a Mud's density with temperature is a function primarily of a Mud's coefficient of expansion. The inventor has found that the expansion over the usual temperature range for the solids phase and the water or brine phase is minimal but the expansion over the usual temperature range for the oil phase is much greater and can be measured.

The inventor has also found that the nature of expansion of SO the Oil phase is very similar to the total Mud expansion.

Of course it is understood this is a surface phenomena at virtually atmospheric pressure. When the Mud is pump down-hole and subjected to pressure greater than atmospheric this relationship may change.

Control of the Mud Weight or Mud Density is vital to safe and efficient drilling. This is normally the responsibility of the so called Rig crew who control the Density by additions of heavy material such as Barites or lighter fluid such as so called base oil or water or operation of so called solids control equipment such as a centrifuge. The Rig crew is normally given a target Density to maintain and this is done by following one of the afore mentioned actions.

The Mud Weight or Mud Density is normally measured using a so called Mud Balance although other instrumentation which measures the Mud Density may also be used. In nearly all case the Mud Weight or Mud Density is measured at or nearly equal to the so called line or circulating or ambient temperature.

This methodology may be a problem as no compensation for temperature is made.

This target Density can be difficult to control as it fluctuates as the Mud heats or cools and these temperature related changes can make proper Density control difficult.

This fluctuation in circulating temperature of the mud is a common and well known phenomenon An example of this is on a particular Mud the Weight changed 16.70 ppg (pounds per barrel) to 16.23 ppg with a 56°C change in temperature. Of course it is understood that each Mud behaves differently and this is only an example of one Mud type's characterics.

A potential way to compensate for this fluctuation is to use the measured Density which is at or near the circulating temperature then calculate it to what it would have been at a fixed or referred temperature. This is generally known as The referred Density although other names could be used.

An example of this might be measuring the Mud Weight at 27°C which is the particular circulating temperature at one instance then calculating what it would have been at 50°C the chosen reference temperature.

Of course it is understood that this reference temperature also known as the referred temperature may be any temperature but normally between 0°C and 100°C When temperature compensation is required this is commonly done using graphical charts usually but not always issued by the Mud supplier.

The inventor has found that chart interpretation of graphs can be slow and inaccurate and difficult to use on the rig site and by the rig site personnel. The inventor has also found some of the rig personnel cannot perform this interpretation.

The inventor has also found that if a device could be provided that would automatically calculate and or display the Mud Weight or Mud Density that compensated for this fluctuation due to changes in the temperature of the circulating Mud and could replace the chart interpretation would be useful.

The inventor has also found that if a device could be provided that would automatically calculate and or display the Mud Weight or Mud Density that compensated for this fluctuation due to changes in the temperature of the circUlating Mud and could replace the chart interpretation and do so in a continuous and near real time manner would be useful.

The inventor has also found that if a device could be provided that would automatically calculate and or display the Mud Weight or Mud Density that compensated for this fluctuation due to changes in the temperature of the circulating Mud and could replace the chart interpretation and be designed in a robust way and be simple to operate and be certified to operate in a so called Zone 1 area would be useful.

The inventor has also found that if a device could be provided that would automatically calculate and or display the Mud Weight or Mud Density that compensated for this fluctuation due to changes in the temperature of the circulating Mud and could replace the chart interpretation and be designed in a robust way and be simple to operate and be certified to operated in a so called Zone 1 area and have visible display of the measured density and the so called referred density would be useful.

The inventor has also found that if a device could be provided that would automatically calculate and or display the Mud Weight or Mud Density that compensated for this fluctuation due to changes in the temperature of the circulating Mud and could replace the chart interpretation and be designed in a robust way and be simple to operate and be certified to operated in a so called Zone 1 area and have visible display of the so called referred density and or the measured density in such a way that these value can be sent electronically to off an site location or locations would be useful.

The inventor has also found it is useful to have a simple system for recalibration available to the rig site personnel such as a potentiometer or some such device for the so called referred weight and or circulating weight. -The inventor has also found it is useful to have a simple system for recalibration that can be operated accurately by the personnel available on the Rig site.

The inventor has found that there is a device commercially available currently manufactured by a company called Emerson with a designation of a 7829 Tuning Fork type Viscometer.

The inventor also found that the 7829 Tuning Fork type Viscometer did not work accurately when monitoring OBM and its output signal had to be routed through a Potentiometer whose use was required to establish the required accuracy. The output and input from the 7829 Tuning Fork type Viscometer is represented on Fig 1-14, Fig 2-14, Fig 3-14, Fig 4-14.

The apparatus has two options for the measurement of Density 1 So called Line or Circulating Density -this is the actual density of the circulating Mud 2 So called Referred Density -this is the actual density from 1 above recalibrated to a fixed referral temperature This Referred density is calculated from the Line Density readings. The 7829 Tuning Fork type Viscometer has an option to use its software using a data matrix which calculates this Referred Density.

As supplied, the 7829 Tuning Fork type Viscometer has no data entered into the matrix. This has to be established by the Inventor with many workshop tests with a wide range of Muds of different properties and characteristics.

The 7829 Viscometer has several options for the use of its output and the Inventor has used 2 of these options.

1 The Line Density 2 The Referred Density The Referred Density is a calculated Mud Density at the chosen temperature and is based on the Line Density which is the Density measure at the ambient temperature of the circulating Mud being used.

The Referred Density calculation is made on the 7829's internal software in the form of a so called matrix although the input data for this software has to be found experimentally.

Of course it is understood that other suitable devices might be available either from Emerson or other manufacturers and the 7829 is used only as an example.

The Inventor has found that the Line Density must be calibrated for a particular Mud and this might change in use over 3 hours or 6 hours or 9 hours or some such periods. If the Line Density must be regularly calibrated then the Referred Density has also be calibrated.

The inventor has concluded that if minimum recalibration operations are required then when The Line Density is recalibrated The Referred Density must also be simultaneously recalibrated.

The inventor has also found field calibration is important and must be a simple process and this can be done with reference to the accompanying drawings Fig 1 shows the Circulating Density display (Fig 1-7) linked (Fig 1-8) to a potentiometer (Fig 1-3) installed on the inlet and output from the 7829 Viscometer (Fig 1-14) with a handle (Fig 1-5) installed. The potentiometer can rotated anticlockwise or clockwise -an example is shown (Fig 1-2). A similar system shows the Referred Density display (Fig 1-1) linked (Fig 1-11) to a potentiometer (Fig 1-lOLinstalled on the inlet and output from the 7829 Viscometer (Fig 1-14) but without a handle. The potentiometer can rotate anticlockwise or clockwise -an example is shown (Fig 1-12). Eoth these potentiometers linked by a so called slave gear (Fig 1-4) which can also rotate -an example is shown (Fig 1-9) but will rotate in the opposite direction to the potentiometers (Fig 1- 205 3 & Fig 1-10) Comparison with Fig 1 and Fig 2 will illustrate how field calibration is performed. The chosen referred temperature is 50°C. The example (Fig 2) shows what the displays should be with a circulating density of 14.45 ppg (Fig 2-7) measured at 210 20°C and the Referred Density of 14.05 ppg (Fig 2-1) at 50°C assuming the device was correctly calibrated.

The actual Circulating Density of the Mud has been established as 14.45ppg. This was established using the so called Mud Balance but the Circulating Density display is showing 14.15 215 ppg (Fig 1-7) . The operator turns the potentiometer (Fig 1-3) clockwise (Fig 1-2) until the Circulating Density display reads 14.45ppg (Fig 2-7). with the slave gear (Fig 1-4) linking both potentiometers (Fig 1-3 & Fig 1-10) when the Circulating Density is calibrated there is also automatic 220 recalibration of the Referred Density.

The inventor has found that the calibration of the most commonly available so called Base Oils used to make the oil phase of an OBM is based on a coefficient of expansion whose graphical gradient is linear and of a similar gradient. Of 225 course it is recognised that not all so called Base Oils will exactly fit the matrix. The nature of the expansion for these other Base Oils will be linear but the gradient might be different. This difference is minimal and within the tolerance of the recalibration system.

230 It may be that an alternative recalibration may be required and this could be performed using one of the options as follows 1 Recalibration of the Matrix on the 7829 or similar device 2 Adjustment of the Slave gear (Fig 1-4) 235 If recalibration of the Matrix is required this will be done experimentally and primarily in the workshop If adjustment of the Slave gear is required this is shown in Fig 3 and Fig 4.

It is of course understood this is an example only and other 240 details may be relevant Fig 3 shows a difference between the Circulating Density and the Referred Density of 0.3lppg but as this is tested with Mud at 50°C which is the same as the referred temperature of 50°C it is incorrect. In this case both displays should have read 245 14.15 ppg. The slave Gear (Fig 3-4) is withdrawn and no longer links the potentiometers (Fig 3-10 and Fig 3-3) so both potentiometers can turn independently. The Referred Density potentiometer (Fig 3-10) is rotated until the display reads the same as the Circulating Density (Fig 3-7) of 14.15 ppg 250 (Fig 4-1) . The slave gear (Fig 3-4) is reinstalled and the link between both potentiometers is re-established and re-calibration is completed.

Of course it is understood the device may or may not require calibration prior to dispatch to the well site.

255 Of course it is understood there might be other systems for

simple workshop or field calibration

Of course it is understood that the handle (Fig 1-5) may be located elsewhere such as Fig 1-9 or Fig 1-10 The inventor has also found that it would be useful if the 260 apparatus could be linked to the so called charge pump which pumps to the main Mud pump. This is when Mud is delivered to the apparatus rather than the apparatus operating as a stand-alone sampling device ---2