3D Seismic Technology
The philosophy of Fossil Oil Company, L.L.C. is that oil and gas reserves are usually discovered at places where 3D seismic exploration techniques and geologic interpretation have been applied in finding solid indications that hydrocarbons exist in the subsurface of the lease tracts to be drilled. Fossil Oil Company, L.L.C. drills only 3D seismic based prospects that reflect the strongest gas and oil seismic signatures.As the wellbore (hole) is drilled, it is lined with steel pipe, called casing that is centered into the hole. Usually, the final string of casing is cemented in place and perforated in order to complete the well. Sometimes, different completion techniques are utilized, depending on the nature of the reservoir and other factors.
Oil can flow out of a reservoir and up the wellbore to the surface because of the difference in pressure caused by connecting the pay zone (sand), through drilling, with the surface. In water-driven wells, saltwater, trapped under the weight of the Continental Shelf, rushes to all areas of less pressure, permeating where possible and collecting the lighter weight oil and gases at the top of traps. As oil and gas are produced, water takes the provided space and eventually the reservoir can become depleted. Even with artificial lift like pump jacks, all of the oil originally in the reservoir will not be recovered. Additional recovery techniques such as water-flooding and miscible processes are able to recover more. Even present-day additional recovery techniques will not recover all of the oil that is in a reservoir (30% or more remains).
Whether the oil flows to the surface through natural energy, artificial lift, or by way of additional recovery techniques, that oil from the reservoir usually has gas, water, and sediment in it. Most of the water and sediment have to be removed before the crude can be sold to a shipper. Also, gas and oil must separate from each other.
Gas wells are connected to a complex pipeline system through a flow-meter that records gas volumes as they enter the pipeline. The meter chart is replaced and submitted for payment each month. Multiple gas wells on a given lease are inter-connected through an onsite infrastructure or "mini-pipeline". Well tests are run on wells throughout their producing lives. Their basic purpose is to assist the well owners in producing their wells efficiently. Some of the tests measure the potential of the well, others measure the bottom hole pressure and temperature, still others indicate the fluid level in a well. Regardless of the test, the ultimate goal is to recover as much oil and gas from a reservoir as possible.
Oil must be temporarily stored on a lease before it is sold to a transportation company. While it is on the lease, oil is accurately tested and gauged, or measured in order to determine its quality and quantity prior to sale.
Finally, some special problems may be encountered on the lease. Corrosion, scale, paraffin, H2S, and saltwater disposal are some problems that must be solved if successful production is to continue
People who explore for oil and gas traps are called Exploration geologists and Geophysicists. Their main job is to find subsurface traps that could contain hydrocarbons.
One of the sciences that geophysicists use in their search for traps is seismology. Seismology is the study of vibrations in the earth. The vibrations take the form of sound waves. For instance, an earthquake creates sound vibrations that can be studied by seismology. Sound vibrations can also be made and studied on the surface of the earth. Man - made sounds can help geophysicists find traps.
To understand these special sounds and how they are used to find tarps, lets look at a simple comparison. Most of us have experienced the sound of our voices coming back to us from the face of a cliff or building. The sound travels through air, bounces off the cliff or wall, and returns back to us as an echo. The use of seismology to explore for petroleum traps is based on the same principal, but it is somewhat different.
In seismic exploration, geophysicists are looking for traps buried deep beneath the surface. So, the sound has to travel not through air but through rock. Also, the sound has to have the right characteristics to go through thousands of feet of rock and back up to the surface. Further, the seismic work of a geophysicist usually covers many miles of surface area in order to increase the chances of finding a potential reservoir.
Regardless of how the sounds are made, they enter the layers of rock below the surface, and each rock layer reflects some of the sound back, just as a cliff reflects the sound of a voice back. These reflections of sound, or echoes, must be heard or detected. Several sensitive detectors called geophones in land exploration and hydrophones in offshore exploration are used to pick up the echoes. On land, the geophones are usually strung out in a line or array behind truck and are connected together with electric cable. The cable goes to recording equipment that is usually housed in a truck. Offshore, the hydrophones are trailed in a line behind a boat, and the boat carries the recording equipment.
In either case, when the reflected sound comes bouncing back from the rock layers, it reaches the geophones (or hydrophones, as the case may be) on the surface. The geophones convert the sound vibrations to electric current, which is sent along the cable to a tape recorder. The tape holds a record of the echoes. In a laboratory, the tapes are played back into computer, and record sections (also called seismic sections) are made. Expert interpretation of record sections - a sort cross section of the earth - can reveal what may be a trap for petroleum.
It is important to realize that exploration techniques only indicate where an oil and gas trap may be. In most cases, record sections do not give any direct indication of the presence of hydrocarbons in a trap. However, a seismic phenomenon known as bright spot shoes up on a seismic section as a sound reflection that is much stronger or weaker than usual. A bright spot sometimes indicates natural gas in a trap. It is safe to say, however, that the only sure way to find out whether hydrocarbons are in a trap is to drill a hole down to it.
Geologists use a different technique for discovering oil and gas traps. Typically, a geologist will take known points of control from well logs of existing wells. With this data, the geologist will plot the wells on a map, noting the presence, thickness, quality and subsurface depths of the various strata. Then, through a combination of experience, knowledge and (to varying degrees) instinct, the geologist extrapolates the data to form a three dimensional picture of what lies between the known control points. These days, most geologist and geophysicists overlap this process using seismic data to confirm their geologically rendered maps or vice versa.