Horizontal Drilling Technology with Cycling Using of Inert Foam
Authors: MENG Y.F. , Lou P.Y. , Jiao D. , Lao R.K. 
Published: December 2007

Abstract
It was introduced in this paper that the research results on Low Pressure Drilling (LPD) technology have been done in Southwest Petroleum Institute (SWPI) for six years. It was pointed out in the paper that the LPD technology, especially combined with horizontal drilling technology, is a very important development in near future. But only through a serious technology modification, the LPD can become a powerful technology. The most bright modifying direction is "Horizontal Drilling Technology with Cycling Using of Special Inert Foam". Special foam drilling fluid is a very important developing direction of drilling fluid technology.

Introduction
In 1989, on a regular seminar about the low pressure drilling hold in SWPI, experts from drilling, well completion, formation damage control and drilling fluids discussed the low pressure drilling technologies. At that time, the research about underbalanced drilling seems stopped in the world. Can underbalanced drilling be a future drilling technology? If it is, what is the direction? After raising these questions, a group of 12 researches was formed to collect the papers and patterns on the technology. Totally, about six hundreds and fifty papers and patterns are reviewed in order to understand the status, development and problems in underbalanced drilling. On the basis of the technology review and petroleum market analysis, the investigation of the developing direction and predictions of underbalanced drilling has been done. The main conclusions are following: the low pressure drilling, especially combined with horizontal drilling technology will be a new powerful drilling technology. However, the underbalanced drilling technology used before needs to be improved in order to become the powerful low pressure drilling technology. In the research report of the low pressure drilling technology, the technologies needed to be improved and their directions are itemized.
In 1991, a group of 25 persons worked on the projects supported by CNPC, Xinjiang and Liaohe oil fields. A research base was set up and 1.5 millions Yan was invested to do the research projects on low pressure drilling technology. The horizontal drilling technology with cycling using of inert foam was developed and now, is using in Liao He oil field.

Why Will The Low Pressure Drilling Be a New Drilling Technology?
Figure la shows the literature and patents on the low pressure drilling for each year. From this Figure we can see that the low pressure drilling started from early 1950s, reached to a peak at 1960s and dropped to a foot at 1980s because of oil price. After entering 1990s, the low pressure drilling technology has been made a progress in North America, we believe that the low pressure drilling technology will be the new drilling technology in near future.
Why does the low pressure drilling technology come up again? In order to answer this question, the initial and future drive forces to develop this technology must be analyzed. Before 1990's this technology was mainly used to increase economical benefits or overcome some drilling difficulties. Such as air drilling, the penetration rate is 4 to 10 times faster than mud drilling and drill bit life is 2 to 3 time longer than mud drilling. The Fig 1b shows the initial drive forces.
In the near future, the petroleum industry faces two challenges. One is the limited petroleum resources and available resources declines, the possibility of finding a giant or big oilfields is very limited in the world.
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