Oil and gas companies are faced with the problem of replacing reserves that are rapidly depleting to meet the growing needs of domestic and US markets. As the cost of replacement is constantly increasing, companies are very interested in any technology that reduces the risk of exploration for oil and gas. Soil gas geochemical exploration is one of those technologies because at minimum cost it can find deep-seated oil and gas reservoirs by detecting their leakage patterns at the surface.

The exploration for oil and gas is such a risky business that companies want as much information as possible before drilling, the most costly stage of the exploration process.

Traditional oil and gas exploration drilling may be divided roughly into three risk categories depending on how far it is from the nearest producing well:

• Wildcat drilling (extremely high risk). This type of drilling is by definition conducted in areas that are greater than 1.5 miles (oil) or 3 miles (gas) from the nearest producing well or at greater depth over known pools. Rank wildcats refer to wells drilled at least ten miles from the nearest producing well. Wildcatting is without question the highest-risk venture in the petroleum industry. Historically, only 6-12 % of wildcat wells find enough petroleum to pay for the drilling. Only 2-3% yields enough petroleum to economically justify drilling of an adjacent well and only 0.15% (1 out of 700) will discover enough petroleum to warrant developing a field.

• Outpost drilling (moderate risk). An outpost well is not as risky as a Wildcat well because it is located closer to the nearest producing well: either 1/2 - 1.5 miles (oil) or 1-3 miles (gas). Geochemisty is far more cost efficient in locating the outer limits of newly discovered fields.

• Developmental drilling (low risk) is conducted at locations that are within 1/2 mile (oil) or one mile (gas) adjacent to wells already drilled. The need for geochemistry is not as acute because the risks are low. However, geochemistry can be extremely useful in finding blind compartments of stratigraphic traps.

As the most costly stage of gas/oil exploration process is the drilling, which can cost up to several million dollars for deep plays, the explorationist tries to reduce his risk by utilizing exploration methods that provide the maximum information at the lowest cost possible before actual drilling.

Seismic exploration is one such method but it too is relatively costly, especially for 3-D. Petro-Find surveys are a fraction of the cost of 2-D single-line seismic surveys.

The Petro-Find method is an excellent low-cost tool to quickly ascertain the oil and gas potential over a wide area and pinpoint areas for focused exploration by seismic and follow-up drilling. Petro-Find uses the soil gas method exclusively because of its high accuracy and repeatability in detecting light hydrocarbons.

High anomalous values of methane and ethane plus in soil gas indicate reservoirs of gas and oil, respectively, directly underneath. Interpretations are based on the fact that all reservoirs leak to a certain extent, essentially in a vertical direction. Petro-Find technology can detect even the smallest amount of light hydrocarbons in soil gas. This sensitivity allows the surface mapping of hydrocarbon reservoirs in highly complex geologic structures such as fluvial valley fills and shelf deposits.

Present day exploration for oil and gas requires a coordinated effort based on the successful integration of geophysics, geology and geochemistry. Geophysical exploration is very expensive and unlike geochemistry it finds only structures, which may or may not contain hydrocarbons. As geochemistry measures total light hydrocarbons, interpretation is required to differentiate between two or more reservoirs of the same composition located directly over each other. On the other hand, it is easy to differentiate between shallow dry gas reservoirs at high pressures and deeper heavy oil reservoirs that are deficient in methane. Surface geochemical prospecting offers the explorationist another overlay of information to reduce risk. Oil seeps, which result from the intersection of oil reservoirs by faults, also provide major clues to the existence of oil.

HOW RISK OF EXPLORATION CAN BE REDUCED

The need for Petro-Find geochemical services depends largely on the success a company wants to achieve as an exploration company. Petro-Find technology can save as well as make $ for a company by assisting it to make timely and informed decisions at every stage of the exploration process from land acquisition to drilling.

The basic approach to any exploration program is to use methods that provide the maximum information at the lowest cost possible. Ideally, geochemistry should be used first followed by seismic then drillling. In this way the financial risk of finding oil and gas is reduced substantially.

The need for Petro-Find soil gas surveys can be be easily gauged by replying to the following questions.