According to analysis of oil production history registered in the state and national databases, during the operation well flow rate is reduced to 10-12 barrels per day and in many cases to zero. There are many causes of the fall production rate: pressure drop in the reservoir, flooding, screening, colmatation (mudding). The actual depletion of productive layer is less common.
Studies have shown, that almost all the main cause is used incorrect “old” methods of primary opening the productive formation, among which stand out bullet perforations in the old wells. Since the late sixties bullet perforations replaced cumulative perforation. Cumulative perforation leads to destruction of productive layer in the wellbore zone, and the subsequent attempts to re-perforation do not give some positive results.
The number of drilled oil and gas wells in the World is huge. Most of the wells are in the United States. Among the millions of working oil wells there are about 400,000 are low-productive or “stripper” wells, most of which produce less than five barrels a day. The age of most low-production wells 60 - 80 or even 100 years, and a large part of them already liquidated (abandoned).
At the same time, during all period of exploitation of the wells in most cases was used no more than 25-35 % of the available stocks. It was established that in vertical wells the hydrocarbon extraction is not more than 40 %, and for horizontal even less. Extraction of oil, mainly confined to the good collectors. More than 70-80 % of the cemented reservoirs contain basic unrecoverable hydrocarbons. Geological and geophysical estimates show that the residual oil reserves are still around 200 billion barrels of oil.
Many service-companies, company-operators and well-owners offer various projects to develop new and re-completion of old low-productive oil and gas wells, for example: www.mergernetwork.com “Five oil wells, but only one work (1 bbl./day), after re-completion we plan to get 10 bbl./day from all five wells”. Anyone can find an acceptable version of the investments in Oil and Gas Industry.
Without going into details of the Geological and Geophysical analyzes they make re-completion with old traditional standard "cosmetic" methods, with very limited choices, and with very doubtful results. It is not possible to apply the same methods of re-completion for all wells. There is no standard treatment for all the wells.
The wells developed by more traditional but less effective methods require reconstruction, and the first step in solving the problem of increase the productive inflows can be re-opening of productive formations using more effective methods of opening casing, cement and productive formation.
□ Well wash
□ Replacement of underground pump, motor or tubing
□ Painting of pump-jack in customer's colors
□ Chemical treatment (possible)
□ Additional cumulative or point-perforation (possible)
□ Additional hydraulic fracturing (possible)
□ Deepening well (possible but difficult)
□ It's all
Buying the well or investing money in re-completion without thorough and detailed Geological and Geophysical analysis, without calculating the residual reserves and financial profits, without defining the main causes of falling production rate and without determining the most effective methods of treatment for increase the flow, it is a purchase "a pig in a poke".
Only when general cause of fall inflow in the well is determined, is possible to take a decision about real and most effective method of treatment on the basis of financial possibilities and the desired effect. The reason for the fall of inflows must be determine first, and only after that is possible to determine the really effective treatment.
Also some service-companies argues, that new drilling of vertical well can cost as low as $ 20-25 thousand dollars. But do not forget, that according to the statistics from ten newly drilled wells begin to work and give productive inflow only two. Also do not forget about casing’s installation, cementation, logging, analysis, casing opening, opening the productive layers, subsequent development of the well, etc. The process of entering the well into operation in several times more expensive than drilling, and no guarantee that you will get good productive inflow. Therefore, the correct restore existing low-producing oil and gas wells less risky and less expensive.
Wells developed by more traditional but less effective methods require a reconstruction, and the first step in solving the problem of increase the productive inflows can be re-opening of productive formations using more effective methods of opening casing, cement and productive formation.