jagomart
digital resources
picture1_Oil Pdf 177183 | Attaoverview


 144x       Filetype PDF       File size 0.17 MB       Source: static1.squarespace.com


File: Oil Pdf 177183 | Attaoverview
environmental management in oil and gas exploration and production 2 overview of the oil and gas exploration and production process the oil and gas industry comprises two parts upstream then ...

icon picture PDF Filetype PDF | Posted on 28 Jan 2023 | 2 years ago
Partial capture of text on file.
                ENVIRONMENTAL MANAGEMENT IN OIL AND GAS EXPLORATION AND PRODUCTION
                  2 Overview of the oil and gas exploration
                         and production process
                The oil and gas industry comprises two parts: ‘upstream’—             then be used to identify promising landscape formations such
                the exploration and production sector of the industry; and            as faults or anticlines. More detailed information is assembled
                ‘downstream’—the sector which deals with refining and pro-            using a field geological assessment, followed by one of three
                cessing of crude oil and gas products, their distribution and         main survey methods: magnetic, gravimetric and seismic.
                marketing. Companies operating in the industry may be                     The Magnetic Method depends upon measuring the
                regarded as fully integrated, (i.e. have both upstream and            variations in intensity of the magnetic field which reflects the
                downstream interests), or may concentrate on a particular             magnetic character of the various rocks present, while the
                sector,  such  as  exploration  and  production,  commonly            Gravimetric Method involves the measurements of small
                known as an E&P company, or just on refining and market-              variations in the gravitational field at the surface of the earth.
                ing (a R&M company). Many large companies operate glob-               Measurements are made, on land and at sea, using an aircraft
                ally and are described as ‘multi-nationals’, whilst other smaller     or a survey ship respectively.
                companies concentrate on specific areas of the world and are              A seismic survey, as illustrated in Figure 1 on page 6, is the
                often referred to as ‘independents’. Frequently, a specific           most common assessment method and is often the first field
                country has vested its interests in oil and gas in a national         activity undertaken. The Seismic Method is used for identify-
                company, with its name often reflecting its national parent-          ing geological structures and relies on the differing reflective
                hood. In the upstream sector, much reliance is placed upon            properties of soundwaves to various rock strata, beneath ter-
                service and upon contractor companies who provide special-            restrial or oceanic surfaces. An energy source transmits a pulse
                ist technical services to the industry, ranging from geophysical      of acoustic energy into the ground which travels as a wave
                surveys, drilling and cementing, to catering and hotel services       into the earth. At each point where different geological strata
                in support of operations. This relationship between contrac-          exist, a part of the energy is transmitted down to deeper layers
                tors and the oil companies has fostered a close partnership,          within the earth, while the remainder is reflected back to the
                and increasingly, contractors are fully integrated with the           surface. Here it is picked up by a series of sensitive receivers
                structure and culture of their clients.                               called geophones or seismometers on land, or hydrophones
                    Scientific exploration for oil, in the modern sense, began        submerged in water.
                in 1912 when geologists were first involved in the discovery              Special cables transmit the electrical signals received to
                of the Cushing Field in Oklahoma, USA. The fundamental                a mobile laboratory, where they are amplified and filtered
                process remains the same, but modern technology and engi-             and then digitized and recorded on magnetic tapes for
                neering have vastly improved performance and safety.                  interpretation.
                    In order to appreciate the origins of the potential impacts           Dynamite was once widely used as the energy source, but
                of oil development upon the environment, it is important to           environmental considerations now generally favour lower-
                understand  the  activities  involved.  This  section  briefly        energy sources such as vibroseis on land (composed of a gen-
                describes the process, but those requiring more in-depth              erator that hydraulically transmits vibrations into the earth)
                information should refer to literature available from industry        and the air gun (which releases compressed air) in offshore
                groups and academia. Table 1 provides a summary of the                exploration. In areas where preservation of vegetation cover
                principal steps in the process and relates these to operations        is important, the shot hole (dynamite) method is preferable
                on the ground.                                                        to vibroseis.
                Exploration surveying                                                 Exploration drilling
                In the first stage of the search for hydrocarbon-bearing rock         Once a promising geological structure has been identified, the
                formations, geological maps are reviewed in desk studies to           only way to confirm the presence of hydrocarbons and the
                identify major sedimentary basins. Aerial photography may             thickness  and  internal  pressure  of  a  reservoir  is  to  drill
                4
                                                                          OVERVIEW OF THE OIL AND GAS EXPLORATION AND PRODUCTION PROCESS
                Table 1: Summary of the exploration and production process
                   Activity                                                              Potential requirement on ground
                   Desk study: identifies area with favourable                           None
                   geological conditions
                   Aerial survey: if favourable features revealed, then                  Low-flying aircraft over study area
                   Seismic survey: provides detailed information on geology              Access to onshore sites and marine resource areas
                                                                                         Possible onshore extension of marine seismic lines
                                                                                         Onshore navigational beacons
                                                                                         Onshore seismic lines
                                                                                         Seismic operation camps
                   Exploratory drilling: verifies the presence or absence of             Access for drilling unit and supply units
                   a hydrocarbon reservoir and quantifies the reserves                   Storage facilities
                                                                                         Waste disposal facilities
                                                                                         Testing capabilities
                                                                                         Accommodation
                   Appraisal: determines if the reservoir is economically                Additional drill sites
                   feasible to develop                                                   Additional access for drilling units and supply units
                                                                                         Additional waste disposal and storage facilities
                   Development and production: produces oil and gas from                 Improved access, storage and waste disposal facilities
                   the reservoir through formation pressure, artificial lift,            Wellheads
                   and possibly advanced recovery techniques, until                      Flowlines
                   economically feasible reserves are depleted                           Separation/treatment facilities
                                                                                         Increased oil storage
                                                                                         Facilities to export product 
                                                                                         Flares
                                                                                         Gas production plant
                                                                                         Accommodation, infrastructure
                                                                                         Transport equipment
                   Decommissioning and rehabilitation may occur                          Equipment to plug wells
                   for each of above phases.                                             Equipment to demolish and remove installations
                                                                                         Equipment to restore site
                                                                                                                                                      5
                 ENVIRONMENTAL MANAGEMENT IN OIL AND GAS EXPLORATION AND PRODUCTION
                   Figure 1: Seismic surveys                                                column of mud or water
                                                                                            with which the shot hole
                                                                                            was tamped
                                  recording truck
                                                                                                     shot firer
                                                                                                                        geophones
                          harder
                        rock layers                                                                                           reflected
                                                                                                                              shock waves
                 exploratory boreholes. All wells that are drilled to discover         ditions,—particularly wind speed, wave height and current
                 hydrocarbons are called ‘exploration’ wells, commonly known           speed. Mobile rigs commonly used offshore include jack-
                 by drillers as ‘wildcats’. The location of a drill site depends on    ups, semi-submersibles and drillships, whilst in shallow pro-
                 the characteristics of the underlying geological formations. It       tected waters barges may be used.
                 is generally possible to balance environmental protection crite-          Land-based drilling rigs and support equipment are nor-
                 ria with logistical needs, and the need for efficient drilling.       mally  split  into  modules  to  make  them  easier  to  move.
                     For land-based operations a pad is constructed at the             Drilling rigs may be moved by land, air or water depending
                 chosen  site  to  accommodate  drilling  equipment  and               on access, site location and module size and weight. Once on
                 support services. A pad for a single exploration well occu-           site,  the  rig  and  a  self-contained  support  camp  are  then
                 pies between 4000–15 000 m2. The type of pad construc-                assembled. Typical drilling rig modules include a derrick,
                 tion depends on terrain, soil conditions and seasonal con-            drilling mud handling equipment, power generators, cement-
                 straints. Operations over water can be conducted using a              ing equipment and tanks for fuel and water (see Figure 2).
                 variety  of  self-contained  mobile  offshore  drilling  units        The support camp is self-contained and generally provides
                 (MODUs), the choice of which depends on the depth of                  workforce accommodation, canteen facilities, communica-
                 water, seabed conditions and prevailing meteorological con-           tions, vehicle maintenance and parking areas, a helipad for
                 6
                                                                                                     OVERVIEW OF THE OIL AND GAS EXPLORATION AND PRODUCTION PROCESS
                           Figure 2: Drilling                                                                         depth of the hydrocarbon bearing formation and the geolog-
                                                                                                                      ical conditions, but it is commonly of the order of one or
                                                                                                                      two months. Where a hydrocarbon formation is found,
                                                                                                                      initial well tests—possibly lasting another month—are con-
                                                                                                                      ducted to establish flow rates and formation pressure. These
                                                                          swivel                                      tests may generate oil, gas and formation water—each of
                                                                                                                      which needs to be disposed of.
                                            mud                                                                            After drilling and initial testing, the rig is usually dis-
                                            pump                            kelly                                     mantled and moved to the next site. If the exploratory
                                                                stand pipe                                            drilling has discovered commercial quantities of hydrocar-
                                                               discharge                                              bons, a wellhead valve assembly may be installed. If the well
                                                  suction                          rotary                             does not contain commercial quantities of hydrocarbon, the
                                                  line                              hose                              site is decommissioned to a safe and stable condition and
                                                                                                   drill pipe         restored to its original state or an agreed after use. Open rock
                                                                     mud return line                                  formations are sealed with cement plugs to prevent upward
                                                                mud                                                   migration of wellbore fluids. The casing wellhead and the
                                                                pit          annulus
                                 shale                                                                                top joint of the casings are cut below the ground level and
                               shaker                                      drill collar                               capped with a cement plug.
                                                                                                  bore
                                                                                    bit           hole
                                                                                                                      Appraisal
                                                                                                                      When exploratory drilling is successful, more wells are drilled
                                                                                                                      to determine the size and the extent of the field. Wells drilled
                      remote sites, fuel handling and storage areas, and provision                                    to quantify the hydrocarbon reserves found are called ‘outstep’
                      for the collection, treatment and disposal of wastes. The camp                                  or ‘appraisal’ wells. The appraisal stage aims to evaluate the
                      should occupy a small area (typically 1000 m2), and be                                          size and nature of the reservoir, to determine the number of
                      located away from the immediate area of the drilling rig—                                       confirming  or  appraisal  wells  required,  and  whether  any
                      upstream from the prevailing wind direction.                                                    further seismic work is necessary. The technical procedures in
                            Once drilling commences, drilling fluid or mud is con-                                    appraisal drilling are the same as those employed for explo-
                      tinuously circulated down the drill pipe and back to the                                        ration  wells,  and  the  description  provided  above  applies
                      surface equipment. Its purpose is to balance underground                                        equally to appraisal operations. A number of wells may be
                      hydrostatic pressure, cool the bit and flush out rock cuttings.                                 drilled from a single site, which increases the time during
                      The risk of an uncontrolled flow from the reservoir to the                                      which the site is occupied. Deviated or directional drilling at
                      surface is greatly reduced by using blowout preventers—a                                        an angle from a site adjacent to the original discovery bore-
                      series  of  hydraulically  actuated  steel  rams  that  can  close                              hole may be used to appraise other parts of the reservoir, in
                      quickly around the drill string or casing to seal off a well.                                   order to reduce the land used or ‘foot print’.
                      Steel casing is run into completed sections of the borehole
                      and cemented into place. The casing provides structural                                         Development and production
                      support to maintain the integrity of the borehole and isolates                                  Having established the size of the oil field, the subsequent
                      underground formations.                                                                         wells drilled are called ‘development’ or ‘production’ wells.
                            Drilling operations are generally conducted around-the-                                   A small reservoir may be developed using one or more of the
                      clock. The time taken to drill a bore hole depends on the                                       appraisal wells. A larger reservoir will require the drilling of
                                                                                                                                                                                                             7
The words contained in this file might help you see if this file matches what you are looking for:

...Environmental management in oil and gas exploration production overview of the process industry comprises two parts upstream then be used to identify promising landscape formations such sector as faults or anticlines more detailed information is assembled downstream which deals with refining pro using a field geological assessment followed by one three cessing crude products their distribution main survey methods magnetic gravimetric seismic marketing companies operating may method depends upon measuring regarded fully integrated i e have both variations intensity reflects interests concentrate on particular character various rocks present while commonly involves measurements small known an p company just market gravitational at surface earth ing r m many large operate glob are made land sea aircraft ally described multi nationals whilst other smaller ship respectively specific areas world illustrated figure page often referred independents frequently most common first country has vest...

no reviews yet
Please Login to review.