Drilling fluid separation

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Drilling fluid separation its environmental
issue

• DESALEGN YESHITILA
• NUGROHO ADI SASONGKO

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• 1. Solid control history2. Functions of drilling
  fluid3. Solids control equipment4.
  Environmental impacts

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• History of solid control
• Drilling fluid maintenance cost, clean up
  disposal cost as well as the over all cost of
  boring, can be reduced dramatically when proper
  solids control techniques are utilized. These
  facts were recognized in the oil industry in the
  late 1800s. When open earthen pits we used to
  separate the cuttings from the borehole. This was
  accomplished by a series of weirs and settling
  pits that allowed the solids to naturally settle
  out by using gravity. The clean mud then flowed
  into a suction pit to be re-pumped down hole.
  This was the first solids control technique ever
  used

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• Functions of drilling mud
• to control subsurface pressures, lubricate the
  drill bit, stabilize the well bore, and carry the
  cuttings to the surface, among other functions.
  Mud is pumped from the surface through the hollow
  drill string, exits through nozzles in the drill
  bit, and returns to the surface through the
  annular space between the drill string and the
  walls of the hole

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• Benefits of low solids in drilling Mud
• Increased drilling penetration
• Increase bit or back reamer life
• Reduce mud cost
• Reduce triplex mud pump, mud
• motor surface equipment
• maintenance cost.
• Reduced clean up haul off or
• disposal cost

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Mud Circulating System
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• Solids removal theory
• Drilling fluid and equipment maintenance cost can
  decrease greatly when proper solids control
  practices are utilized. From a fluid control
  stand point it would be desirable in most cases
  to remove all drilled solids. Although this is
  possible, it would be cost prohibitive. The goal
  of a solids control system is to achieve the
  balance between mechanical solids separation and
  dilution that will result in drill solids being
  maintained at an acceptable level with a minimum
  of cost

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• Particle size and effects
• - Drilled solids are those particles that enter
  the mud system in the form of cuttings from the
  bit or back reamer or from borehole debris. These
  solids vary in size from less than one micron
  larger depending on the carrying capabilities of
  the drilling fluid.
• - Drilling fluid is classified as water base
  utilizing water as the liquid phase. The solid
  phase of any drilling fluid is either commercial
  solids or drilled solids. Most commercial solids
  such as bentonite have a relative particle size
  of less than one micron. (.000039 inches).

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• Methods of controlling solids
• Mechanical treatment
• Chemical treatment
• Dilution of mud with water
• Discard mud mix new mud

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• Mechanical separation basics
• Mechanical separation equipment employs mass
  differences, size differences or a combination of
  both to selectively reject undesirable solids and
  retain desirable drilling fluid.  The desanders
  and desilters utilize centrifuge force and mass
  difference between the solids density and liquid
  density for solids removal. The shale shakers
  employ a vibrating screen of various micron-sized
  differences.

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• Basic Equipment of Mud Solid Control
• Shale shaker
• Desander
• Desilter
• Hydrocyclone
• Mud cleaner

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• Shale shaker
• One method of removing solids from drilling mud
  is to pass the mud over the surface of a
  vibrating screen. Particles smaller than the
  openings in the screen pass through the holes of
  the screen along with the liquid phase of the
  mud. Particles too large to pass through the
  screen are thereby separated from the mud for
  disposal. Basically, a screen acts as a
  go-no-go gauge  Either a particle is small
  enough to pass through the screen or it is not.

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• Decanter

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• Hydrocyclones
• Hydrocyclones are simple mechanical devices, with
  out moving parts, designed to speed up the
  settling process. Feed pressure is transformed
  into centrifugal force inside the cyclone or cone
  to accelerate particle settling in accordance
  with Stokes Law 1. In essence, a cyclone is a
  miniature settling pit which alloys very rapid
  settling of solids under controlled conditions.

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Environmental Issue of drill cutting
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• During drilling operations, two types of drilling
  waste are created
• Cuttings (rock mass) and useddrilling mud.
  Drilling fluid will always be attached to
  cuttings. The industry uses three types of
  drilling
• fluids, all with different technical and
  environmental properties. The authorities
  requirements related
• to the disposal of waste are linked to the
  following properties
• Oil-based drilling fluids (OBM) Have in most
  cases the best technical properties. The
  authorities
• do not permit the discharge of OBM and cuttings
  drilled with oil-based drilling fluids. Cuttings
  and
• fluids are taken to shore.
• Water-based drilling fluids (WBM) The
  authorities permit the discharge of used drilling
  fluid and
• cuttings upon application.
• Synthetic drilling fluids (SBM) Based on ether,
  ester or olefin. They have technical properties
  that
• are similar to oil-based drilling fluids in many
  ways. Discharge of used SBM is not permitted, but
• the discharge of cuttings may be permitted upon
  application.
• The use of water-based drilling fluids has
  increased by 20 per cent from 2005. There have
  not been
• any reports of the use of synthetic drilling
  fluid in 2006, while the use of oil-based
  drilling fluids has
• been reduced by 16 per cent.

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• Treatment of drill cutting
• Discharge (Offshore)/Disposal to sea - If the
  cuttings are considered low environmental risk
  and depending on local regulations, they can be
  disposed into the sea in certain regions.
  However, most require some pre-treatment to
  reduce the oil-on-cuttings to less than 6.9 by
  volume on a wet weight basis.
• 2. Transportation to Shore
• Injection - In the injection process, the
  cuttings are converted into slurry,
• which is then pumped into a receiving
  formation at pressures exceeding the fracture
  gradient.

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Environmental Issue
The dryness of the cuttings aids disposal or
re-use.
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• Drill Cutting Transportation

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• In previous picture is shown the new designed
  platform supply vessel ST216 with 8 integrated
  structural tanks under deck for drill cutting of
  total abt. 430 m3. Number of tanks can be
  adjusted to suit actual capacity requirements.
• To day handling of drill cutting give a potential
  hazard to following
• Possible pollution to sea through disposal on
  sea bed
• Potential spillage to sea
• Safety risk for personnel through extensive
  manual handling and lifting operations.
• Safety risk to personnel and vessel in cases
  where transported DC may be classified as
  hazardous cargo containing low flash point
  substances.

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QUESTIONS ?