Offshore Drilling Mud solids control

The drilling fluid called mud only looks like mud. Actually, it is a complex mixture of water or oil, clays, and chemicals. It's composition and properties have been carefully studies and tested. The study is closely associated with chemistry, math, and physics. The term mud refers technically to a suspension of solids in water or oil, while drilling fluid is a broader term including air, gas, water, and mud.

Drilling fluid is the more appropriate term for including all types of fluid used, but term mud is preferred the field for in naming the most common type. The drilling mud basically perform the following functions:-

1. Removal of Cuttings

2. Control Formation Pressure

3  Prevent Caving

4. Caking off Per. Formations

5. Suspension of Cuttings

6. Release of Cuttings

7. Cooling & Lubrication

8. Formation Damage

9. Formation Evaluation

10. Corrosion

Common types of mud used are :

1. Polymer Muds - incorporating generally long-chain, high-molecular-weight polymers are utilized to either encapsulate drill solids to prevent dispersion and coat shales for inhibition increasing reducing loss inhibition, or for viscosity and fluid loss.

Various polymers are available for these purposes, including acrylamide,cellulose and natural gum-based products. Frequently, inhibiting salts, such as KCl or NaCl, are used to provide greater shale stability. These systems normally contain a minimum amount of bentonite. Most polymers have temperature limits below 300°F, but under certain conditions, may be used in wells with appreciably higher BHTs.

2. Oil-based muds. Oil-based systems are used for a variety of applications, where fluid stability and inhibition are necessary, such as high-temperature wells, deep holes, and where sticking and hole stabilization are problems. They consist of two types of systems:

a. Invert emulsion muds are water-in-oil emulsions, typically with calcium chloride brine as the emulsified phase and oil as the continuous phase. They may contain as much as 50% brine in the liquid phase. Relaxed, invert emulsion muds are a “relaxed” emulsion, and have lower electrical stabilities and higher fluid-loss values. Concentration of additives and brine content/salinity are rheological, filtration and varied to control emulsion stability.

b. Oil-based muds are formulated with only oil as the liquid phase and are often used as coring fluids. Although these systems pick up water from the formation, no additional water or brine is added. All oil systems require higher additional gelling agents for viscosity. Specialized oil-based mud additives include: emulsifiers and wetting agents (commonly fatty acids and amine derivatives) for high molecular weight viscosity; high-molecular-soaps; surfactants; amine treated organic materials; organo clays and lime for alkalinity.

3. Synthetic muds. Synthetic fluids are designed to mirror oil-based mud performance, without the environmental hazards. Primary types of synthetic fluids are esters, ethers poly alpha olefins and isomerized alpha olefins They are esters, ethers, olefins. environmentally friendly, can be discharged offshore, and are non-sheening and biodegradable.

Mud weight, or density, is the weight per unit volume of the mud. With simple water base mud a mud, density can be regarded as measure of the suspended solids.

Excessive solids can:
􀂾 cause wear on pumps bits drill strings; and 􀂾retard penetration rates;
􀂾cause a thick filter cake to be deposited on permeable formations;
􀂾cause fluids loss to the formation;
􀂾causes unnecessary work for the pump, having to push unwanted weight in the circulating fluids.


Solids Control

Offshore Marine Project Management

Offshore and Marine projects are generally large scale and their production is spread over several years. The planning of these projects is therefore diverse, and covers a wide range of activities. The cost implication is also very huge and risky and critical of management control over the overall design and construction phase. Cost, material, logistic and resources control are going to be very dynamic in such kind of projects.

Several levels of planning are usually identified.

Corporate Planning, which looks at the long term future of the whole company. A corporate plan may look five years ahead, and include major investment plans, product changes and other important issues. It is usual for the planning of a marine project to be done within the framework set by the Corporate Plan. In some cases, where small ships are built in a generally shorter timescale or in the case of repair and conversion companies, the Corporate Plan may have a shorter timescale. But there should be some idea of where the company is heading

For a company engaged in a number of offshore marine projects, the corporate plan may need to correspond to some recognisable programme management. Selection of the most appropriate projects and their co-ordination is important.

Strategic Planning, covering the duration of a project :

The strategic plan for a project has a timescale determined by the timescale of the project. For a typical ship this is about two years as the time between contract and delivery. Again the plan may have a longer or shorter duration depending on the project size.

Strategic planning is essentially a network plan for the construction of the ship (which may be likened to a civil engineering project in that it takes place usually on a fixed site to which the parts of the ship are moved.

Tactical Planning, covering the next few months in a department :

At this level the focus moves from a network plan to departments, which may be organised on batch or flow production lines. The tactical plan is a response to the demands set by the strategic plan. The tactical plan often includes work for several projects which are running in parallel.

Detailed Planning, covering the next few weeks for a work station :

The detailed plan is essentially a schedule for the individual work stations. This attempts to strike a balance between the internal efficiency of the work station activities and the need to produce parts and other items to a timetable which will allow the overall project timescale to be maintained.

The project plan is not limited to the production activities, but must also include technical elements, curement and other pre-production functions.

In order for a offshore or marine vessel to be produced, a number of key questions need to be answered.

What is to be produced?

When is it to be produced?

Where is it to be produced?

With what resources?

How will it be produced?

The production of a marine or offshore vessel depends on the generation of a large set of information. Historically, technical departments were concerned primarily with function, and other information was developed within the production departments.

Now most of the information is developed within technical and other departments,and must be included in the project planning and management process. The Korea and China yards are now applying Mega blocks concept to speeding up their construction processes and thus shortening the project lead time compared to other developing countries yards.

 
MAR8102 Marine Proj Mgt Post School

More on marine systems design...

Introduction to basic marine system concepts

• The various duties of an marine engineer relate to the operation of the ship or offshore rig in a safe, reliable, efficient and economic manner. The main power and propulsion machinery installed will influence the machinery layout and determine the equipment and auxiliaries installed. It includes the number of personnel on board in which the auxiliary services and living quarter onboard will provide the necessary comfort to the crew.  Hotel systems provide the hotel facilities. Examples are cabins, galley equipment, laundry equipment, drinking water systems and waste disposal systems.

• Support systems provide the support function, e.g: electric power supply systems, hydraulic power supply system, lubrication oil system and compressed air system.

• Operational systems provide the operational functions, e.g: cargo-handling and conditioning systems, combat system, fishing gear or oil drilling equipment or other specific vessel system.

• This will further determine the operational and maintenance requirements for the ship and thus the knowledge required and the duties to be performed by the marine engineer.

• A vessel or offshore rig is designed to perform a certain operational task: The mission of the vessel determines which functions are needed on board. Ship systems provide these functions. If necessary a system may be categorised into subsystems and ultimately into components. Example, the power, controls, heating and cooling, etc.

marine service system functions.doc 

Marine Systems

Ship Systems

This article briefly shows some typical ship's ancillary services. These info are well applicable not only at concept stage but also during basic design when actual components have not yet been chosen.

Auxiliary oil fired boiler

-Steam production ability:

Saturated steam, 7bar g, 170°C.
1 kW corresponds to about 1,6kg/h steam or
1 MW corresponds to about 0,42kg/s steam

-Fuel oil (FO) consumption:
1,0kW corresponds to 0,105kg of HFO/h
1,0kg/h steam corresponds to 0,066kg of HFO/h

Fuel oil systems

- Main engine (ME) and auxiliary engine (AE) fuel oil consumption
Normally engine suppliers give the specific fuel oil consumption (SFOC) based on ISO 3046/1 standard.

Emergency diesel generator :

SFOC: typical value 0,25kg/kWh
100 kW of power means about 28-litre fuel oil consumption per hour.
FO tank to be dimensioned at least for 36 h constant running according to SOLAS.

Heavy Fuel Oil (HFO) Tanks :

Storage tanks-
Minimum temperature in storage tanks depends on the pour point of the HFO. The temperature of HFO should always be kept higher than pour point to avoid filter blocking, and other similar problems.

Settling tanks-
To allow reasonable separation the tank should be sized for 24h consumption.
The settling temperature to be calculated to be about 70degC.
According to the latest SOLAS rules double settling tanks are needed.

Service tanks-
Service tanks should be sized for 10h - 12h consumption.
The temperature in service tanks to be calculated to be 75°C.

According to the latest SOLAS rules two separate service tanks are needed.

Lubrication oil systems:

- Lubrication oil consumption

LO consumption for medium speed engines in average is about 1,0g/kWh.
-System oil tanks

In case main engines are so-called dry sump engines, there should be a system oil tank on the double bottom.


Sewage systems:


It is highly recommendable to specify a biological sewage treatment plant for all types of ships because of the environmental reasons, further reading required on latest Marpol MEPC159(55) requirement. The plant is typically dimensioned to treat full black water load.

Galley waste water is normally not led to sewage treatment plant, because it slows down the biological process.

Grey waters have been discharged directly overboard or collected to grey water storage tanks. Some times grey waters have been chlorinated before discharging overboard but not really biologically or chemically treated onboard.

Other systems not described could be referred to below slides or will be continued in next blog article.

Ship Designs - General Info

Exhaust Emission (IMO Marpol)

The IMO’s Marine Environmental Protection Committee (MEPC) met at its 57th session from 1 March to 4 April 2008. During the session, both the revised Annex VI of MARPOL and the revised NOx Technical Code were approved, with the intention to adopt the two at the 58th MEPC session, scheduled to take place in October 2008. The annex and the code are then expected to enter into force in Feb/Mar 2010.

The new revision substantially tightens the NOx and Sulphur limits compared to the existing annex, and also includes requirements governing NOx emissions from ships constructed from 1 January 1990 to 1 January 2000.

New NOx limits :

The revised NOx regulations contain a 3-tier approach as follows:

Tier I (identical to today’s limits) :-

For diesel engines installed on ships constructed from 1 January 2000 to 1 January 2011, the allowable NOx emissions are:

-17.0g/kWh when n is less than 130 rpm

-45.0*n(-0.2) g/kWh when n is 130 rpm or more but less than 2000 rpm

-9.8 g/kWh when n is 2000 rpm or more

Tier II  :-

For diesel engines installed on ships constructed on or after 1 January 2011, the allowable NOx emissions are:

-14.4g/kWh when n is less than 130 rpm

-44.0*n(-0.23) g/kWh when n is 130 rpm or more but less than 2000 rpm

-7.7 g/kWh when n is 2000 rpm or more

Tier III :-

Ships constructed on or after 1 January 2016 will have additional limitations when operating in an Emission Control Area (ECA). No ECAs have yet been designated for NOx emissions, but it is expected that both the Baltic Sea and North Sea will be designated as NOx ECAs well ahead of 1 January 2016.

For Tier III ships operating in the NOx ECAs, the allowable NOx emissions are:

- 3.4g/kWh when n is less than 130 rpm

- 9.0*n(-0.2) g/kWh when n is 130 rpm or more but less than 2000 rpm

- 2.0 g/kWh when n is 2000 rpm or more

It should be noted that the Tier III limits cannot be achieved without additional means, such as Selective Catalytic Reduction (SCR) and Water Injection.

NOx Emission Limits for Engines Installed on Ships Constructed Prior to 1 January 2000

Ships constructed on or after 1 January 1990 but prior to 1 January 2000 will be required to comply with the NOx emission limits in force today (Tier I). However, the requirement has been narrowed down to apply to engines with a power output of more than 5000 kW and a per cylinder displacement of 90 litres or above. Moreover, compliance is only required if an Approved Method for obtaining the necessary NOx reduction is available for the engine(s) in question. The regulations also contain a mechanism to ensure that an Approved Method meets a cost-effectiveness criterion which will set a maximum cost for purchasing and installing a method.

Necessary engine adjustments or the fitting of NOx-reducing kits must take place no later than the first renewal survey that occurs 12 months or more after approval of an applicable method. However, if the supplier of an Approved Method is not able to deliver this at the time of this renewal survey, installation may take place at the next annual survey. Detailed requirements for the approval of NOx-reducing methods have been included in the revised NOx Technical Code.

New Limits for Sulphur Content in

Fuel Oil

The new limits for sulphur content in fuel oil will be:

Globally :-

3.50% from 1 January 2012

0.50% from 1 January 2020

In SECAs :-

1.00% from 1 March 2010

0.10% from 1 January 2015

Sulphur scrubbing will still be an acceptable method for compliance and there will be no HFO ban.

In order to confirm that the refinery industry can meet the demand for low sulphur fuels by 2020, a review clause has been introduced scheduling a fuel availability review to be completed by 2018. If this review reveals that it is impossible to meet the 0.50% limit by 2020, the requirement will be postponed until 1 January 2025.

Marine Exhaust Emission