Reservoirs petroleum

In efforts to increase and extend production from oil and gas fields, as well as to keep wells operational, petroleum engineers pump a wide variety of fluids into the subsurface. Fluids are injected into petroleum reservoirs for a number of purposes, including  

In each of these procedures, the injected fluid can be expected to be far from equilibrium with sediments and formation waters. As such, it is likely to react extensively once it enters the formation, causing some minerals to dissolve and others 

There is considerable potential, therefore, for mineral scale, such as barium sulfate (see the next section), to form during these procedures. The scale may be deposited in the formation, the wellbore, or in production tubing. Scale that forms in the formation near wells, known as formation damage, can dramatically lower permeability and throttle production. When it forms in the wellbore and production tubing, mineral scale is costly to remove and may lead to safety problems if it blocks release valves. 

In this chapter, in an attempt to devise methods for helping to foresee such unfavorable consequences, we construct models of the chemical interactions between injected fluids and the sediments and formation waters in petroleum reservoirs. We consider two cases the effects of using seawater as a waterflood, taking oil fields of the North Sea as an example, and the potential consequences of using alkali flooding (i.e., the injection of a strong caustic solution) in order to increase oil production from a clastic reservoir. 

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In Section 5.2.8 we shall look at pressure-depth relationships, and will see that the relationship is a linear function of the density of the fluid. Since water is the one fluid which is always associated with a petroleum reservoir, an understanding of what controls formation water density is required. Additionally, reservoir engineers need to know the fluid properties of the formation water to predict its expansion and movement, which can contribute significantly to the drive mechanism in a reservoir, especially if the volume of water surrounding the hydrocarbon accumulation is large. 

Amyx, Bass Whiting, (1960), Petroleum Reservoir Engineering - Physical Properties, McGraw-Hill... 

Porous Media Packed beds of granular solids are one type of the general class referred to as porous media, which include geological formations such as petroleum reservoirs and aquifers, manufactured materials such as sintered metals and porous catalysts, burning coal or char particles, and textile fabrics, to name a few. Pressure drop for incompressible flow across a porous medium has the same quahtative behavior as that given by Leva s correlation in the preceding. At low Reynolds numbers, viscous forces dominate and pressure drop is proportional to fluid viscosity and superficial velocity, and at high Reynolds numbers, pressure drop is proportional to fluid density and to the square of superficial velocity. 

Natural Gas Natural gas is a combustible gas that occurs in porous rock of the earth s crust and is found with or near accumulations of crude oil. It may occur alone in separate reservoirs, but more commonly it forms a gas cap entrapped between petroleum and an impervious, capping rock layer in a petroleum reservoir. Under high-pressure conditions, it is mixed with or dissolved in crude oil. Natural gas termed dry has less than 0.013 dmVm (0.1 gaLlOOO fF) of gasoline. Above this amount, it is termed wet. 

In the 1840s, America s first petroleum reservoir was discovered in Tarentum, Pennsylvania. By the late 1850s, lubricants and kerosene were being extracted commercially from crude oil. 

Petroleum engineers are traditionally involved in activities known in the oil industry as the front end of the petroleum fuel cycle (petroleum is either liquid or gaseous hydrocarbons derived from natural deposits—reservoirs—in the earth). These front end activities are namely exploration (locating and proving out the new geological provinces with petroleum reservoirs that may be exploited in the future), and development (the systematic drilling, well completion, and production of economically producible reservoirs). Once the raw petroleum fluids (e.g., crude oil and natural gas) have been produced from the earth, the back end of the fuel cycle takes the produced raw petroleum fluids and refines the.se fluids into useful products. 

Burcik, E.J., Properties of Petroleum Reservoir Fluids, International Human Resources Development Corp., Boston, 1979. 

Manipulating a petroleum reservoir during enhanced oil recovery through remote sensing of proeess data, development and use of dynamic models of underground interactions, and selective injection of chemicals to improve efficiency of recovery ... 

Standard programs must be broken into smaller pieces to run on a hypercube. Each processor is assigned the responsibility for calculations for a specific piece of a problem. For example, in petroleum reservoir simulation, each processor might be assigned a different section of the reservoir to model. In modeling a complex chemical plant, each processor might be assigned a different piece of equipment. As each processor proceeds, it informs the other processors of its results, so that all the other processors can incorporate the information into their respective portions of the overall calculation. 

The coinjection of growth-effective nutrients into the extreme environments that characterize petroleum reservoirs [1604]... 

Koedritz LF, Harvey AH, Honarpour M (1989) Introduction to petroleum reservoir analysis. Gulf, Houston... 

The computer interface system lends itself well to the determination of interfacial tension and contact angles using Equation 3 and the technique described by Pike and Thakkar for Wilhelmy plate type experiments (20). Contact angles for crude oil/brine systems using the dynamic Wilhelmy plate technique have been determined by this technique and all three of the wetting cycles described above have been observed in various crude oil/brine systems (21) (Teeters, D. Wilson, J. F. Andersen, M. A. Thomas, D. C. J. Colloid Interface Sci., 1988, 126, in press). The dynamic Wilhelmy plate device also addresses other aspects of wetting behavior pertinent to petroleum reservoirs. 

Increasing the water-wet surface area of a petroleum reservoir is one mechanism by which alkaline floods recover incremental oil(19). Under basic pH conditions, organic acids in acidic crudes produce natural surfactants which can alter the wettability of pore surfaces. Recovery of incremental oil by alkaline flooding is dependent on the pH and salinity of the brine (20), the acidity of the crude and the wettability of the porous medium(1,19,21,22). Thus, alkaline flooding is an oil and reservoir specific recovery process which can not be used in all reservoirs. The usefulness of alkaline flooding is also limited by the large volumes of caustic required to satisfy rock reactions(23). 

Actual responses of tuo carbonate petroleum reservoirs to matrix injection of hydrochloric acid are compared with a recently proposed experimental model for wormholing. This model is shown to be applicable in undamaged primary porosity reservoirs, and should be useable in damaged double porosity ones. Formations of no primary porosity are shown to respond very differently. 

Paralleling the corrosion problem is one involving compatibility of any well fluid with nonmetallic materials used in well completion apparatus. All injection wells and many producing wells are equipped with packers to isolate the casing annulus from the high temperature, pressure, and salinity characteristic of the petroleum reservoir environment. Conventional packers, as well as other well tools, utilize elastomeric materials to mechanically seal appropriate locations. 

Fig. 2.8. Example of a flush model. Fluid is pumped into a petroleum reservoir as a stimulant, or industrial waste is pumped into a disposal well. Unreacted fluid enters the formation, displacing the fluid already there.

Petroleum reservoirs, however, occur in a gray facies of the Lyons found in the deep basin (Levandowski et al., 1973). This facies contains no ferric oxides... 

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