In this article, we will familiarize ourselves with the concept of reservoir pressure (PD). Here the questions of its definition and significance will be raised. We will also analyze the method of human exploitation. We will not ignore the concept of abnormal reservoir pressure, the accuracy of the measuring capabilities of the equipment and some individual concepts associated with the dominant in this text.
Introduction
Reservoir pressure is an indicator of the magnitude of the pressure created by the action of reservoir fluids and displaced on a particular rock of minerals, rocks, etc.
Fluids are any substances whose behavior during deformation can be described by using the laws of mechanics for liquids. The term itself was introduced into the circulation of the scientific language around the middle of the seventeenth century. They designated hypothetical fluids, with the help of which they tried to explain from a physical point of view the formation of rocks.
Formation definition
Before proceeding with the analysis of reservoir pressure, attention should be paid to some important concepts that are associated with it, namely: the reservoir and its energy.
Geologists call a layer a body with a flat shape. At the same time, its power is much weaker than the size of the distribution area within which it acts. Also, this power indicator has a number of homogeneous features and is limited to a set of parallel surfaces, both small and large: the roof is the top and the sole is the bottom. The definition of a power indicator can be determined by finding the shortest distance between the sole and the roof.
Reservoir structure
Layers can be formed from several layers belonging to different rocks and interconnected. An example is a coal seam with existing mudstone layers. Often the terminological unit “layer” is used to designate stratified accumulations of minerals, such as coal, ore, oil, and aquifers. The formation of layers occurs by superimposing on each other various sedimentary rocks, as well as volcanic and metamorphic rocks.
The concept of reservoir energy
Reservoir pressure is closely related to the concept of reservoir energy, which is a characteristic of the capabilities of reservoirs and the fluids contained in them, for example: oil, gas or water. It is important to understand that its value is based on the fact that all substances inside the formation are in a state of constant voltage due to rock pressure.
Species diversity of energy
There are several types of reservoir energy:
- pressure energy of reservoir fluid (water);
- energy of free and liberated gases in solutions with reduced pressure, for example, in oil;
- elasticity of compressed rock and fluid;
- pressure energy due to the gravity of a substance.
During the selection of fluids, in particular gas, from the reservoir environment, energy is consumed to ensure the process of fluid movement, through which they can overcome the forces opposing their movement (forces responsible for internal friction between liquids and gases and the rock itself, as well as capillary strength).
The direction of movement of oil and gases in the reservoir space, as a rule, is determined by the manifestation of new types of formation energy simultaneously. An example is the emergence of elastic energy of rock and fluid and its interaction with the potential of the gravity of the oil. The predominance of a certain type of energy potential depends on a number of geological features, as well as the conditions under which a deposit of a particular resource is exploited. Correspondence of a specific form of energy, with the help of which the movement of liquids and gases is carried out, with the type of a producing well, allows distinguishing between different operating modes of gas and oil deposits.
The importance of the parameter
Reservoir pressure is an extremely important parameter that characterizes the energy capabilities of reservoirs that carry water or oil and gas resources. In the process of its formation, several types of pressure are involved. All of them will be listed below:
- hydrostatic reservoir pressure;
- excess gas or oil (Archimedes force);
- pressure, which occurs due to changes in the size of the volume of the tank;
- pressure due to expansion or contraction of fluids, as well as a change in their mass.
The concept of reservoir pressure includes its two different forms:
- Initial - the initial indicator that the reservoir had before opening its reservoir underground. In some cases, it can be preserved, that is, not disturbed due to the influence of technogenic factors and processes.
- The current, which is also called dynamic.
If we compare the reservoir pressure with the conditional hydrostatic (pressure of a column of fresh fluid, altitude from the daily surface index to the measurement point), then we can say that the first is divided into two forms, namely, anomalous and normal. The latter is directly dependent on the depth of the beds and continues to grow, approximately 0.1 MPa for every ten meters.
Normal and abnormal pressure
PD in the normal state is equal to the hydrostatic pressure of the water column, with a density equal to one gram per cm 3 , from the formation roof to the earth's surface vertically. Abnormal reservoir pressure is any form of pressure manifestation that differs from normal.
There are 2 types of abnormal PD, which will now be discussed.
If the PD exceeds hydrostatic, i.e., in which the pressure of the column of water has a density index of 103 kg / m 3 , then it is called abnormally high (AVP). If the pressure indicator in the reservoir is lower, then it is called abnormally low (ANPD).
An abnormal PD is in an isolated type system. At present, there is no single answer to the question about the genesis of APD, as here the opinions of experts differ. Among the main reasons for its formation are such factors as: the process of compaction of clay rocks, the phenomenon of osmosis, the catagenetic nature of the transformation of rocks and organic compounds included in it, the work of tectogenesis, as well as the presence of a geothermal environment in the bowels of the earth. All these factors can become predominant among themselves, which depends on the structure of the geological structure and the historical development of the region.
However, most researchers believe that the temperature factor is the most important reason for this or that formation formation and the presence of pressure in it. This is based on the fact that the thermal expansion coefficient of any fluid in an isolated rock is many times higher than the same index for the mineral series of components in mountain rocks.
Setting ADF
The ADF is established as a result of drilling in various wells, both on land and in the waters. This is due to the constant search, exploration and development of gas and / or oil deposits. They are usually found in a rather large range of depth levels.
Where it is extremely deep at the bottom, you can often find abnormal high reservoir pressure (from four km or more). Most often, this pressure will exceed hydrostatic, approximately 1.3 - 1.8 times. Sometimes there are cases from 2 to 2.2; in such cases, they are most often unable to exceed the geostatic pressure exerted by the weight of the overlying rock. It is extremely rare to find a case in which at a great depth it is possible to fix a pressure drop equal to or greater than the value of geostatic pressure. It is assumed that this is due to the influence of various factors, such as: an earthquake, a mud volcano, an increase in the salt-dome structure.
Positive component of the PDA
AVPD has a beneficial effect on the reservoir properties of the host rock. It allows you to increase the time interval for the exploitation of gas and oil fields, without the use of secondary expensive methods. It also increases the specific gas supply and well flow rate, tries to maintain hydrocarbon accumulation and is evidence of the presence of various isolated areas in the oil and gas basin. Speaking about any forms of PD, it is important to remember from what it is formed: reservoir pressure of gas, oil and hydrostatic.
Places with AAPs that were developed at great depths, especially in places with regional distribution, contain a significant reserve of such a resource as methane. He is there in a state of solution, which is contained in superheated water, with a temperature of 150-200 ° C.
Some data
A person can extract methane reserves and use the hydraulic and thermal energy of water. However, there is also a downside here, because AAPD often become sources of accidents that occurred during well drilling. For such zones, a weighting method is used in the drilling process, the purpose of which is to prevent the release. However, the solutions used can be absorbed by two-pressure formations: hydrostatic and abnormally low.
When comprehending the process of extracting oil and gas resources through the installation of towers, you need to know about the concept of bottomhole pressure. It is the magnitude of the pressure at the bottom of an oil, gas or water well that completes the work process. It should be below the value of the reservoir magnitude of the impact.
General information
PD constantly changes as the formation spreads and the depth of oil or gas deposits increases. It also increases due to an increase in the thickness of the aquifer. Such pressure is compared only with any one plane, namely, the level, the initial position of the oil-water contact. The performance of instruments such as a pressure gauge shows results only for zones of reduced type.
Speaking specifically about the reservoir pressure of the well, then these words mean the amount of accumulation of minerals located in the voids of the earth. The reason for this phenomenon was the accidental presence of the ability of the main part of the formation to surface. The process of formation drinks is carried out, thanks to the holes formed.
SPPD
The reservoir pressure maintenance system is a technological complex of equipment that is required for the preparation, transportation and injection of an agent that performs the force necessary to penetrate the reservoir space with oil. Now we proceed directly to the specifics.
Maintaining reservoir pressure is performed by a system including:
- objects for various types of downloads, for example, water inside the reservoir;
- preparation of intake water to a condition of condition;
- supervision of water quality in RPM systems;
- monitoring the fulfillment of all safety requirements, as well as checking the level of reliability and tightness in the device of the operation system of the industrial water conduit;
- the use of the water treatment cycle in a closed form;
- creation of opportunities for changing the parameters responsible for the mode of water injection from the well cavity.
SPPD in itself carries three main systems: injection for a well, pipeline and distribution, and agent injection. Equipment for the training of the agent used for injection is also included.
Formation pressure formula: Rpl = h▪r▪g, where
h is the height of the liquid column balancing PD,
r is the value of the density of the fluid inside the well,
g is a measure of acceleration in gravity m / s 2 .