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0 2007-04-20 Viorel Vladut V.V. T. Hedison TH R.G. Hollamby RGH Initial Document

Rev Date Prepared by Initials Checked by Initials Approved by Initials Modifications

Form: A62.1858-ADM-FRM-0203 Cegelec 2006 Page 1 of 6

This document is the property of Cegelec (The Company). Distribution and use of this document are strictly governed by the Co mpanys Document Management Policy and Procedures. The contents and form of the document are the sole property of The Company and may not be reproduced, distributed or used without the express written permission of The Company.

Lesson Handout Notes

24331WATER DISPOSAL

A62.1858-LHN-PRO-24331-01

Effective Date: April 20th2007

Training Program : TECHNICIAN: LEVEL 2 CERTIFICATION

Discipline : PROCESS

System : WATERTREATMENT

Sub-System : WATER DISPOSAL

Training Focus : BASIC KNOWLEDGE

Training Elements : This lesson targets training on the following training elements:Disposal Water Quality SpecificationRe-injectionDumping - Water Quality

Training Objectives : At the end of the Lesson the participants will be able to:List typical water quality properties for surface disposalDescribe re-injectionDefine disposed water quality specifications

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DOCUMENT INFORMATION

TABLE OF CONTENTS: Page no.

Technician Level 2 Certification 1

Process 1

Water Treatment 1

Water Disposal 1

Basic Knowledge 1

Document information 2

Table of Contents 2

Purpose 2

Owner 2

Custodian 2

Introduction/Water Quality 3

Water Disposal 4

Water Re-injection 5

Purpose

The purpose of this document is to provide the participant study information.

Owner

The owner of this document is the Process Discipline Team of Ogere Training Facility, Ogere Remo,

Ogun State, Nigeria.

Custodian

The custodian of this document is the Data Administrator and Document Controller of the Ogere TrainingFacility, Nigeria.

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Introduction

Water fit for human consumption is called drinking water or "potable water". Water that is not fit fordrinking but is not harmful for humans when used for food preparation is called safe water.

In the developing world, 90% of all wastewater still goes untreated into local rivers and streams. Some50 countries, with roughly a third of the worlds population, also suffer from medium or high water stress,and 17 of these extract more water annually than is recharged through their natural water cycles. Thestrain affects surface freshwater bodies like rivers and lakes, but it also degrades groundwaterresources. Humans require water that does not contain too many impurities. Common impurities includemetal salts and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable fortaste enhancement and to provide needed electrolytes. The single largest freshwater resource suitablefor drinking is the Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean.

Water Quality

This is the physical, chemical and biological characteristics of water. The primary bases for suchcharacterization are parameters which relate to drinking water, safety of human contact and for health ofecosystems. The vast majority of surface water on the planet is neither potable nor toxic. This remainstrue even if sea water in the oceans (which is too salty to drink) isn't counted. Another general perceptionof water quality is that of a simple property that tells whether water is water pollution or not. In fact, waterquality is a very complex subject, in part because water is a complex medium intrinsically tied to theecology of the Earth. Industrial pollution is a main cause of water pollution.

The complexity of water quality as a subject is reflected in the many types of measurements of water andWastewater quality indicators. These measurements include (from simple and basic to more complex):

Electrical conductivity (also see salinity)

Dissolved Oxygen | Dissolved Oxygen

pH

Color of water

Taste and odor (geosmin,2-methylisoborneol (MIB), etc)

Turbidity

Total suspended solids (TSS)

Chemical oxygen demand (COD)

Biochemical oxygen demand (BOD)

Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia

Lamblia

Nutrients and the environment (fertilizers: nitrates, phosphates)

Dissolved metals and metalloids (lead, Mercury (element), arsenic, etc.)

Dissolved organics: Colored Dissolved Organic Matter (CDOM), Dissolved Organic Carbon(DOC)

Temperature

Pesticides

Heavy Metals

http://en.wikipedia.org/wiki/Geosminhttp://en.wikipedia.org/wiki/Geosmin

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Reclaimed water, sometimes called recycled water, is former wastewater (sewage) that has been treatedand purified for reuse, rather than discharged into a body of water. In some locations, it is treated to becleaner than standard drinking water, and is used indirectly for drinking. In other locations, it is onlyintended to be used for non-potable uses, such as irrigating golf courses and parks, filling decorativefountains, fire fighting, and irrigating crops that will be peeled or boiled before being consumed.

In a basic sense, reclaimed water is treated effluent that is treated to a higher degree (depending on thelocation), instead of being discharged into a natural body of water, and used for a broad range ofpractical purposes. The treatedeffluent fromwastewater treatment facilities is typically dischargeddirectly into a stream, river, or other natural body of water. This recharges the water supply andpromotes the naturaldecomposition of materials in the water that standard treatment practices would notnormally be able to remove. But due to increasing population and increasing demand for reliable freshwater sources, many areas around the world are now using reclaimed water to decrease potable waterdemands.

Water Disposal

The purpose of Produced Water Degasser is to separate any remaining oil and hydrocarbon gases fromthe produced water before disposal. It is a three-phase separator and it receives produced water fromthe Oil / Water Hydrocyclone. There is very little difference between a phase separator and a degassingdrum except for the internal layout. A degasser drum normally runs at a very low pressure and it has aninternal bucket for collecting any small amounts of oil produced its main function is as its name suggeststo free any gas from the produced water.

Feed from the hydrocyclone enters the degasser; it is entering a larger space allowing the fluid toexpand to its natural size. Due to the effects of density difference between the fluids and gases and theaction of gravity the gas will naturally separate from the water, collects at the top of the vessel and is fedaway to the flare system.

Oil will naturally float on water and settle to the top of the liquid, this is then skimmed over and iscollected in the bucket area to be fed back to the sump collection or pumped to the LP separator. Cleanwater builds up in the inlet base of the vessel and travels to the opposite end from the inlet to spill over aweir system and then to disposal.

It should be noted that the feed from the hydrocyclones should already be in high quality specificationsand the oil and gas content very low before the action of the degasser. Oil is separated from theproduced water by gravity and the gases that flash-off flow to the LP Flare Header. The clean producedwater is then pumped for disposal (see Figure 1).

Figure 1Produced Water to Disposal

http://en.wikipedia.org/wiki/Effluenthttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Decompositionhttp://en.wikipedia.org/wiki/Decompositionhttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Effluent

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Water Re-injection

The volume of water strata in an oil production reservoir is controlled by re-injecting separated water intothat water stratum. A production string is extended into a portion of a wellbore that extends laterallywithin the oil strata of the reservoir. A liquid flow including a hydrocarbon phase and a water phase isconducted from the oil strata into the laterally extending portion of the wellbore at a production zone. Thewater phase is separated from the liquid hydrocarbon phase within the production string, and then re-injected back into the water strata of the same reservoir from which it came, at a re-injection zonedisposed below the production zone.

Produced water, formation water or brine as it is sometimes referred to, is comprised of water containingresidual hydrocarbons, heavy metals, numerous inorganic species, suspended solids and chemicalsused in treatment and hydrocarbon extraction. It is a byproduct of the cleaning process of raw crude fromthe well head. Figure 2 shows the typical process layout.

Figure 2Water Injection Process Layout

Water injection is typically done for 2 reasons:

1. Disposal of water recovered from the raw crude oil/water emulsion separation process.

2. Enhances oil recovery by maintaining formation pressure and displacing the crude oil in thereservoir.

Raw production, from the wellhead, comes typically in the form of a mixture of free water, oil/wateremulsion, oil and solids. This combination is also referred to as BS&W (basil sediment and water) andoil. The raw production from the wellhead is then piped to gathering points, known as satellites. Fromthere it is piped to the production facility or battery.

This raw production then enters the Free Water Knockout Vessel (FWKO) where the free water andloose solids are separated from the remaining oil/oil-water emulsion and stored in the produced watertanks. The remaining oil/oil-water emulsion then proceeds to the treater vessels where a combination ofheat and chemicals (emulsion breakers) are used to break the emulsion and produce clean oil andproduced water and solids.

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Clean oil then proceeds to storage or shipping. The produced water from the treaters is transferred totanks to hold for disposal. Depending on residence time in the tanks, some of the solids may settle out ofthe water and residual oil in the water floats to the surface. This oil layer is skimmed off the top and

recycled through the plant to recover this additional oil. In smaller production facilities, this water may bedisposed of directly from the tanks. In larger facilities, there is often an additional water treatment vesselknown as a dissolved air flotation (DAF) unit that further cleans the water.

After the DAF unit, the water is either sent through filters, which are usually sand or multimedia filters orthrough hydrocyclones to remove the last traces of oil. After final filtration, the water is used for steamgeneration, discharged to agricultural canals or rivers or re-injected downhole.

As oil wells mature, the ratio of water to oil increases. This is because the formation waters out due tothe water injection process. Water becomes a significant byproduct of oil and gas production. Forexample more than 7m3of water is produced for every cubic meter of oil or gas equivalent.The produced water is disposed of by either re-injection or by discharge into the environment.

Subsurface injection is the primary method for disposal of produced water for land-based oil and gasoperations. Produced water may be re-injected for disposal to shallower saltwater formations, or re-injected to older, depleted producing formations. By injecting the water into the producing formation,(Water Flood) well pressure and product flow is maintained by displacing the produced oil.