MUD ENGINEERING GUIDELINES ON THE RIG

Author: Boma Femi Julius Category: Mud Engineeering Guides

FIRST DAY ON THE RIG

 

  • Obtain the mud program and drilling program from the Project Engineer/company man.

REASON: This is the mud engineers Bible on the rig. It is based on prior knowledge of all drilling parameters and gives you a step by step plan for present well being drilled. It would guide you all though the drilling process.

 

  • Study your silos, pits, mud tanks, storage tank names, its contents, volume, dead volume capacity, properties of their contents (mud: especially Mud weight).

REASON: You don’t want to be taken unawares, you need to know the type of mud you have in each pit (where your backup mud is, kill mud if any, premix, etc.), you need to be sure you have enough mud to reach TD (Total depth) most especially if the logistics of transporting mud to the rig n’est pas facile, or takes days to arrive. Finally without knowing the properties of the mud you are introducing to the active system you would not be sure if what is affecting your active mud system is coming from the formation or from the mud you are introducing to the active mud.

 

  • Familiarize yourself with the flow lines, mix lines, dump valves, bypass valves etc.

REASON: If there’s going to be a rig operation such as displacement, or cement job that requires you to bypass fluids to different pits or dump fluids (to avoid contamination) you need to know your lines and valves and where it leads to before such operations.

 

  • Obtain the shaker screen inventory upon arrival of any rig from the store man or tool pusher or whoever is in charge or create one if none is available.

REASON: You need to be sure you have enough screens to TD the well and spud the next well also. Place order for screens if short of screens, consider screens for the next section or next well if you have the storage space for it.

 

  • Check physical Chemical/Lab inventory.

REASON:  The earlier you know the chemicals/lab reagents/equipments that are physically on ground or those you lack the earlier you can order for them and avoid downtime. Also confirm that you have relevant minimum contingency chemicals (10% of actual chemical stock is suitable).

 

REASON: You need to be sure you have enough weighting agent to kill the well if you take a kick. At least minimum of 45-100 MT is the required amount for contingency.

 

SUBSEQUENT DAYS ON THE RIG

 

  • Read all previous emails (at most 1 month) relating to the drilling operation.

REASON: 90% of all correspondence to the rig mud engineer comes via email.

 

  • When called, attend pre-job safety meetings before any major operation on the rig.

REASON: Specific hazards would be identified and discussed before any major rig operation, this keeps you safe.

 

  • When drilling commences: Be at the shakers anytime drilling commences for a new well, or a new section, after a displacement, after a trip, etc

REASON: You need to be sure the shaker screens can handle the flow if the mud is cold if not temporarily screen down to a lower size mesh or ask the driller to reduce the flow rate if permissible.

Prior to starting with OBM soak screens in Base fluid, or use a spray gun.

 

  • Always enquire if a slug would be required before every trip/wiper trip.

REASON: Drilling fluids would normally splash the rig crew on the rig floor while pulling and racking back pipes when a stand is removed from the drill string. So a slug (same mud but with 2-2.5 ppg higher density) would be prepared in the slug tank, and pumped into the drill string. This keeps the fluids level inside the drill pipe below the surface when tripping drill pipe.

 

  • Always make contributions to the drilling operation when you can.

REASON: The mud engineer is the expert of his own field and knows his job better than anyone else on the rig.

 

  • Before you receive mud/bulk products from mud plant, measure your initial mud tank volume/air gap or silo gauge readings before and after receiving.

REASON: That’s how you calculate your volume received.

 

  • Always do a mud check when you receive mud from the mud plant, supply vessel, vacuum truck etc

REASON: Mud properties written on the DT (delivery Ticket) might not be exactly as stated so confirm.

 

  • Keep an eye on mud losses (surface and formation).

REASON: The mud is yours you need to be accountable for it.

 

  • For a leak off test (LOT), the mud has to be circulated to obtain uniform weight and condition. The primary concern for the mud engineer is to ensure an equal mud weight all through the mud. Mud weight going in to the hole should be equal to mud weight coming out of the hole at the shakers.

REASON: You would get inaccurate LOT result if your mud weight is not consistent throughout the system.

 

  • When drilling, most especially a pressure zone or a wild cat well, there should be no direct fluid transfer to the active pit.

REASON: The well needs to be properly monitored. Instead speak with the mud loggers to convert the pit you want to transfer fluid from to the active system from a Reserve pit to an Active pit on their system then you can gradually make your transfers that way all volumes would be shown as active pit volume.

 

  • Be at the Shakers to identify fluids during displacement.

FOR DISPLACING FROM WBM TO OBM, OR FROM OBM TO BRINE

Use pump stroke calculation.

REASON: This gives one a heads up.

 

Use Electric Stability Meter.

REASON: It’s used to measure the relative stability of a water-in-oil emulsion. With increase of water, the E.S drops this would be a clear indication of WBM coming on surface, same the other way round, with decrease of water the E.S value climbs. But before the displacement take the initial E.S values of the concerned fluids so as to have an idea what to expect.

 

Use a mud balance.

REASON: If the amount and average specific gravity of the solids in both fluids (i.e. the density) are different the mud weight would be a good indicator of the fluids interface during a displacement.

 

Use Volume calculation

REASON: Calculate your hole volume, that means equal amount of mud on surface will leave you pit, so get the derrick man or personnel assisting you in the pit room to inform you when hole volume has been pumped.

 

DISPLACING FROM UNFILTERED BRINE TO FILTERED BRINE

Use pump stroke calculation.

REASON: This gives one a heads up.

 

Use physical Observation.

REASON: Viscosified HEC pill spacer pumped before the filtered brine should be easy to identify/describe by touch due to the viscosity differences.

 

Use Visual Observation

REASON: Filtered brine should contain particles no greater than 2 microns and are solids free, so they can be visually inspected for clarity using a beaker

 

Use a Nephelometric Turbidity Unit (NTU).

REASON:  Using a technique called nephelometry the turbidity can be measured. When light hits a particle the energy is scattered in all directions, it measures the level of light scattered by particles at right angles to the incident light beam. Initial NTU readings of both fluids would be the reference point for identification. After the Hi-vis passes through the driller should be told to stop pumping when the initial NTU of the filtered brine has been achieved.

 

Use Volume calculation

REASON: Same above for using volume calculation.

 

CEMENT DISPLACEMENT.

Use pump stroke calculation.

REASON: This gives one a heads up.

 

Use Electric Stability Meter

REASON: The stability of the emulsion drops with increase of water as the cement spacer approaches surface, spacer can then be bypassed and you need to justify/account for fluids dumped or bypassed by reporting the E.S value (E.S Value from 50 – 100 can be bypassed).

 

Use phenolphthalein droplets.

REASON: To identify traces of cement contamination on surface to be bypassed.

For water based mud with a low alkalinity use phenolphthalein also. Add it to the mud and check for change of color to pink to know when traces of cement are on surface.

 

Use a mud balance.

REASON: Note differences in weight between mud, spacer and cement before displacement of cement. The mud weight difference between the three fluids is a good indicator of the fluids interface on surface.

 

  • Condition mud prior to logging, running casing or cement Job before pulling out of hole Drill pipe.

REASON:  The first step is removal of cuttings from the borehole and the drilling fluid after which the mud should be condition before placing cement in the wellbore, either the density (not compromising well control) or the rheology depending on the situation. For the rheology, the yield stress, gel strength and plastic viscosity would be reduced hence reducing the driving forces necessary to displace mud with increased mud flexibility while being careful to prevent barite settling.

 

  • For a Cement job, the pit level should be recorded at all stages during a cement job.

REASON: With no pit space to store the equivalent mud volume being replaced down hole, all pit levels should be recorded at all stages during the cement job. You would need to visit the pit room and return to the cement unit (while measuring cement density) at appropriate moments.

 

Procedure:

Measure all tank volumes before cement job i.e. when the mud has been thinned down and pump has been stopped (pit static). In case of leaks or valve mistakes all pits should be recorded.

Measure all tank volumes after spacer has been pumped when pits are static just before pumping cement commences.

Measure all tank volumes when a tail slurry is being mixed with pits static after the lead has been pumped.

Measure all tank volumes after pumping cement before displacing with mud.

Finally measure all tank volumes after the plug is bumped and displacement has come to an end.

If we get full returns during cementing it means that the cement displaced equal amount of mud and there was no loss down hole due to the cement job or due to displacement.

 

  • Prior to running casing, calculate the displacement of the casing first to know the volume it would displace, calculating from the mud line up to the casing depth.

REASON: There would be returns to the pit while running in hole casing, so set a pit ready to receive the displacement from the casing and measure its volume or measure the entire surface volume in case of any fluids transfer in your absence. Trace the losses, Get the current depth (measured Depth), and measure all the pits, when you know the subsequent increment of the pit it should tally with the displacement of the steel, i.e. if there are no losses.

 

  • If tripping is done you can calculate the displacement of the drill string by checking your pit volume before tripping and after tripping.

REASON: Also to check for losses.

 

  • Before a cement job request for cement program from the company man.

REASON: From the cement program calculate the total volume of the fluids /cement that would be pumped into the hole that is not mud so as to confirm tank space to receive equal volume from the hole. If no available tank space/storage space then OBM should be back-loaded before the cement job to create space.

 

  • Meet the company man / Directional Driller for confirmation prior to pumping certain grades /type or concentrations of LCM pills.

REASON: If it’s the pay zone, losses would require the use of acid-soluble LCM to prevent formation damage. Also considering down hole tools and motors, certain concentrations of LCM pills would not be pumped to avoid plugging/damaging the tools unless a bypass tool is part of the BHA.

 

  • Be at the shakers 5 minutes before a sweep pumped hits surface.

REASON: To check effectiveness of such sweep /estimate percent increment in cuttings.

 

  • Visit the shakers regularly while drilling and at TD.

REASON: To observe nature of cuttings while drilling- If cuttings are round, splintered, tabular, marshy, brittle, if no cuttings, if shakers are clean at TD prior to pulling out of hole. After your assessment of the cuttings then you decide what action to take.

 

  • Don’t get run off:

REASON: hmmmm………

 

 

Despite all the guides what is most important is that the mud program is followed as every well drilled has its own uniqueness.

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