JONATHAN RAMSEY • Oil and Gas production occurs after a well is drilled. • Managing Oil and Gas production by exploration and production companies involves actions to optimize production from Oil and Gas wells, which includes Well maintenance, Well intervention, Well workover or repair, and improved oil recovery methods such as secondary recovery and tertiary recovery techniques. Start of Production: • Before well production starts the rig and other equipment that is used to drill is moved away. TRUE or FALSE • A Christmas tree is installed on the wellhead of a well. TRUE or FALSE • What does the valves on a Christmas tree do? These valves regulate pressures, control flows, and allow access to the wellbore in case further completion work is needed. manage fluid flowing from the well. • Look at the diagram of a typical Christmas tree below: There are several configuration types. • Let’s identify the valves on a typical Christmas tree from the bottom up. Valves from the bottom left and right hand sides are Primary and Secondary kill line valves; and Primary and Secondary choke line valves respectively (closed during well production). Next is the Master Gate Valve, next are two Primary and Secondary Wings vales on the Left and Right hand side with an Adjustable choke valve ate the at both ends. Next valve on top is the Swab Valve. • Wing valves and Adjustable choke valves are used to control flow. • Swab valve is closed and opened only to access the well with i.e. wireline for well workover • The other valves expect for kill and choke line valves are always left open during well production. • When the Wing valves and choke valves are used to control floe, they create a backpressure which affects the wellhead pressure (pressure of the well at the surface). • Production tree is another name for a Christmas tree? YES • Hydrocarbon flow from Christmas tree outlet valve (wing valves) are connected to pipelines, processing equipment and tanks; processed fluids can be stored (Oil) or moved to refineries or oil export terminals and natural gas can be moved through pipeline and compressor stations to Gas plants or LNG plants. A typical Christmas tree wellhead configuration. • High reservoir pressure is desired in well, but it is not always available. • Normally reservoir pressure will drop as reservoir fluids are produced. • Normally if there is an increase in bottom hole pressure inside a wellbore, which can also include a drop in reservoir pressure an artificial lift method can be used to maintain well a production. • Secondary recovery and tertiary recovery techniques are used to maintain reservoir pressure when reservoir starts to decrease in other to maintain w ell production. Artificial Lift • The pressure difference between the reservoir pressure and the pressure inside a production well (bottom hole pressure) allows for Oil and Gas to move from the reservoir into the wellbore to be produced at the surface. • The natural pressure or reservoir pressure for a well depends on the fluid type in the reservoir (Gas, Liquid i.e. Oil or/and Water) • This reservoir pressure in Gas and Oil wells helps move reservoir fluid into the wellbore from a higher pressure within the reservoir to a lower pressure area in the wellbore. • Most production wells especially Oil wells experience a decrease in reservoir pressure as production increases. • Artificial lift can be used to lower the bottom hole pressure in this wells, when they start experiencing a decrease in reservoir pressure in other to ensure a continuous movement of reservoir fluids into the wellbore to maintain production. • Typical artificial lift systems that can be installed on a well are sucker rod pumps, Gas-lift systems, Electrical submersible pump systems, Hydraulic submersible pump systems, hydraulic pumping systems and Progressive cavity systems. • State two things that can happen later on after initial production from Oilwell (Oilwell that contain Gas, Oil and Water)? water (which is heavier than oil and much heavier than gas) begins to encroach into the formation; and reservoir pressure drops as the reservoir depletes. • What will happen in a well that experience the problems form your answer above, and there was not a plan to have an artificial lift system for the well? flow from the well will eventually stop • State at least two factors that will affect the selection of an artificial lift system for a well? Reservoir pressure and well productivity • The sucker rod pumping unit (pump jack) has sucker rod (downhole part of rod) connected to a pump downhole and polished rod (surface part of rod) that connects the horsehead on the surface. The movement of the horsehead up and down allows for pumping of reservoir to the surface. See Fig 7.1 for a typical sucker rod pumping unit. • Gas-lifting uses compressed gas most commonly injected in the annulus between a tubing and casing through gas-lift valves located in a mandrel that is made up to the tubing. The injected gas mixes with liquid (Oil/Water) in the tubing to lighten (decease the density) of the liquid and allows for easy flow of the mixture to the surface. If the well produces gas, then less gas will be injected from the surface. Also, high pressure gas from a near-by gas well can also be no need for a compressor or compressor with a lower horse-power. • Electric submersible pumping has a downhole pump at the bottom of the well tubing that is powered by an electric cable from the surface. Reservoir fluid is pumped by the downhole pump from the bottom of the wellbore to the surface. • Hydraulic submersible pumping uses high pressure hydraulic fluid to power the downhole pump at the bottom of the well tubing. Reservoir fluid is pumped by the downhole pump from the bottom of the wellbore to the surface. • Hydraulic pumping systems: this involves pumping hydraulic fluid down inside a tubing to force the reservoir fluids to move upward through the casing/tubing annulus to the surface. • A general method that can be used are dropping soap sticks to mix with liquid (i.e. water) downhole which helps decrease the reservoir fluid density to allow for easy flow upwards. • Another general method that can be used is installing a smaller-diameter tubing sections as part of the tubing which increases gas velocity inside the reduced inside diameter thereby allowing it to remove more water as it flows upwards. • As a summary, when a well starts producing more water than usual and as well as decreasing reservoir pressure in most cases, which leads to the presence of water at the bottom of a wellbore. It becomes difficult to produce Oil from the well without using an artificial lift method to help move the oil to the surface. A typical ESP system See lecture 8 Presentation CH_7 _Part 2(Managing Oil and Gas Production) on Workover of a Well, Improved Oil Recovery, Gas Production Management – an overview and Other Environmental Issues in Gas Production. Also, refer to pages 117 to 129 in textbook. Complete the following exercise. • List the two types of secondary recovery techniques or methods that can be used to improve oil recovery from an Oil?WaterFlood and Gas Injection • Which of the two secondary recovery techniques is widely used and can recover about 5 to 50% of remaining oil in a reservoir?Waterflood • An injection well is needed for both secondary recovery methods. TRUE or FALSE • List the three main types of tertiary recovery or enhanced recovery methods. chemical flooding, gas injection and thermal recovery. • What are the types of thermal recovery that are used to enhance oil recovery methods? Steamflood or steam drive .Steam-assisted gravity drainage. Fireflood • Which of this thermal recovery method will recover the highest percentage of remaining oil in a reservoir? Steam-assisted gravity drainage • Why will you process and treat associated and non-associated gas in a Gas Plant? Removal of carbon dioxide and hydrogen sulfide, Removal of water vapor, Removal of heavier hydrocarbon gases • List the by-products form gas processing and treatment plants that can be used in other industries. Butane, propane • If non-associated gas that flows through a pipeline to a Gas Plant contains acid gases and nitrogen, the acid gases (Carbon dioxide and Hydrogen sulfide) is removed after nitrogen. TRUE or FALSE • Recovered water that contains salt from a Gas Plant is not treated before it can re-used or disposed? TRUE or FALSE • When Oil and Gas production ends from both offshore and onshore wells, the first step is to cut and remove the casing form the wells; and wellbore is plugged up
