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Present day exploration for oil and gas requires a coordinated effort based on the successful integration of geophysics, geology and geochemistry. Petro-Find geochemical soil gas surveys can assist E&P companies to substantially improve their success ratios in hydrocarbon exporation and reduce risk at all stages of the exploration cycle. They can be used in conjunction with seismic surveys to identify drilling targets. However, ideally soil gas surveys should be conducted prior to seismic because of their relatively low cost and ability to rule out at an early stage areas of little interest. Seismic surveys can find structures that appear to be excellent traps but are often found to be dry when drilled. Dry holes are usually due to either lack of charging or breaching of previously charged reservoirs allowing hydrocarbons to escape. Oil seeps, which result from the intersection of oil reservoirs by faults, can also provide major clues to the existence of oil.
The contribution of geochemical surveys to increased discovery ratios can be ascertained by comparing geochemical results with subsequent drilling. "A review of 2774 U.S. and international exploration wells -all drilled after completion of micro seepage surveys - documents that 82% of wells on prospects with a microseepage anomaly were completed as oil or gas discoveries; in contrast only 11% of wells drilled on prospects with no seepage anomaly resulted in a discovery. When hydrocarbon microseepage data is properly acquired and interpreted, it can significantly reduce exploration risks and costs by improving success rates and shortening development time." (Source: D. Schumacher; Search and Discovery Article #400943 (2012). It should be noted that "Dry" means dry or non-commercial; "Discovery" means the well resulted in a commercial discovery. The geochemical methods used included free soil gas, sorbed soil gas and microbial,as well as two geophysical methods, radiometric and micro-magnetics.
Oil and gas companies are faced with the problem of replacing reserves that are rapidly depleting to meet the growing needs of world 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. Seismic exploration is another method but it is relatively costly, especially for 3-D. Petro-Find surveys are a fraction of the cost of 2-D single-line seismic surveys. 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.
The discovery ratio can reach a higher plateau by integrating 3D and other seismic methods with soil gas surveys. This type of survey is the only feasible low-cost tool for assessing the oil and gas potential of large areas, acting as a precursor to 3D seismic surveys. It is well recognized that 3D seismic has made a major contribution to the increase in the discovery ratio in the last decade or so. However, seismic never has been a suitable tool for reconnaissance nor for the evaluation of large areas with little exploration, mainly because of costs. It also has major limitations such as imaging of thin or deeply-dipping reservoirs. A new sophisticated seismic technology - digital, full-wave technolgy - promises to overcome many of the shortcomings of 3D, but it too would benefit from precursor soil gas surveys as it too is not suitable as a reconnaissance tool.
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.
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.
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 drilling. In this way the financial risk of finding oil and gas is reduced substantially. Here are some ways to obtain as much information as possible about hydrocarbon/uranium projects to minimize risk and increase success ratios:
Confirm before drilling whether seismic structures are charged with hydrocarbons.Good seismic structures are often found to be dry.
Find out before drilling whether the target formation contains gas, condensate or oil and whether more than one petroleum system exists. Why drill a well for gas if it has to be capped until the market for gas recovers?
Prioritize the best drilling targets in conjunction with seismic.
Confirm whether a discovery is in the optimum location.
Narrow down the search in large frontier areas with reconaissance surveys. Anomalous trends are defined by high-density surveys as well as seismic.
Evaluate properties before farm-in and farm-out.
Find stratigraphic and other types of hydrocarbon traps invisible to seismic.
Find hydrocarbon traps with poor seismic signal due to sandy overburden and thick salt formations.
Explore for non-conventional gas reservoirs where seismic does not work
very well.
Find edges of pools instead of using offset drilling.
Evaluate mature oil reservoirs for infill potential and bypassed compartments.
Assess the efficiency of secondary/tertiary recovery operations.
Access areas such as community pastures, fields in crop and environmentally sensistive areas without causing surface damage.
Sample wet sediments for hydrocarbons with passive samplers.
Explore for oil and natural gas associated with helium using helium as a pathfinder.
Find bypassed plays and lost compartments in monitoring CO2EOR projects for surface leakage of CO2 and hydrocarbons.
Use stable isotope analysis of carbon and hydrogen in methane to determine whether the gas is microbial, mixed microbial/thermogenic, wet thermogenic or dry thermogenic.
Explore in populated areas where seismic is not feasible.
PETRO-FIND GEOCHEM LTD
215 Mallin Crescent
Saskatoon, Saskatchewan, Canada S7K 7X3
Contact: Paul Lafleur, President
Phone: (306)931-3156 Fax: (306)931-9773
E-Mail: plafleur@sasktel.net