The Philosophy of Searching for Oil is a famous paper in the history of world oil. American petroleum geologist Wallace? Pratt pointed out in this paper: "In the final analysis, the first place to find oil is in people's minds. Wallace believes that to continuously discover oil in new areas, we must first emancipate our minds.
Whether developing ultra-low permeability reservoirs or developing conventional reservoirs, reserves must be available first. In March 2008, Changqing Oilfield started the development of ultra-low permeability reservoirs. In a short time, thousands of people from oilfield companies participated in the development of ultra-low permeability reservoirs. Coupled with the market-oriented drilling, oil testing and surface engineering teams, the number of people blocking ultra-low permeability reservoirs has reached more than 30 thousand. At this time, the proven ultra-low permeability reservoir reserves in Changqing Oilfield are only 20 million tons. Even according to the proportional relationship between the production and construction scale of conventional reservoirs and the proven reserves, the proven reserves of 20 million tons are only enough to build the production capacity of 200,000 tons to 300,000 tons. At this time, if the proven reserve of 20 million tons is a chicken, Changqing Oilfield is obviously holding a butcher knife-people who don't know will definitely think so.
But as Wallace said, the ultra-low permeability reservoir with huge reserves has been found in the minds of decision makers in Changqing Oilfield. The present Ordos basin is formed by the Ordos ancient land. Since 3.6 billion years, there have been no major geological changes such as faults, orogeny and earthquakes in Ordos ancient land. In other words, loess and desert are still buried in a whole rock. This rock, which covers an area of 370,000 square kilometers, inclines to the west, showing a monoclinic shape, just like a big slate obliquely inserted into the ground. In the past 3.6 billion years, bedrock and sedimentary rocks have been superimposed on each other, forming a unique river delta sedimentary system in Ordos Basin. Early Jurassic reservoir in Changqing Oilfield belongs to structural reservoir, just like potatoes buried in the beach. Ultra-low permeability Triassic reservoir belongs to lithologic stratigraphic reservoir, just like a beach buried underground. It's hard to find potatoes on the beach! It is much easier to find a beach in the river. Therefore, when someone said that Changqing Oilfield killed the chicken with a cow knife, the exploration experts in Changqing Oilfield confidently said that the estimated proven reserves of ultra-low permeability reservoirs were 65.438+700 million tons.
At the same time, submitting proven reserves requires a lot of investment. At that time, it was generally believed that ultra-low permeability reservoirs had no development value, so why invest? Therefore, in exploration and evaluation, once this kind of reservoir is encountered, it will not be further studied. As a result, it is known that ultra-low permeability reservoirs have large reserves, wide distribution and overlapping multi-layer systems, but no one can tell exactly how many reserves there are.
Changqing people who have the courage to attack never give up their dream of developing ultra-low permeability reservoirs. In 2005, an important scientific research project was launched in this oilfield, which was called "0.3-millidarcy reservoir development technology research", referred to as "0.3mD". On the basis of summarizing the successful development experience of ultra-low permeability reservoirs, some positive results have been achieved. The dream of effective development of ultra-low permeability reservoirs is approaching step by step, but the contradiction of high input and low output has not been fundamentally solved.
The effective development of ultra-low permeability reservoirs is not and cannot be a purely technical problem, just like the development of Sulige gas field. On August 26th, 2000, well Su-6 obtained a high-yield gas flow with an open flow of 6,543.8+0.2 million cubic meters, which announced the birth of Sulige gas field. In the following years, Sulige gas field with low permeability, low pressure and low abundance carried out a series of development evaluation and technical tests. Although some progress has been made, the contradiction between high input and low output is still acute, and gas field development has come to a standstill.
In 2005, according to the instructions of Jiang Jiemin, the general manager of the group company, Changqing Oilfield adopted the 5+ 1 cooperation model and introduced the market competition mechanism. Through a series of technical and management innovations, Sulige gas field, which has been silent for several years, has finally regained its vitality and achieved large-scale effective development. In 20 10, the output of Sulige gas field exceeded 10 billion cubic meters.
The development of ultra-low permeability reservoirs is as important as Sulige development in Changqing's "Building Daqing in the West and Realizing 50 Million Tons", and it also faces the contradiction of high input and low output. The development of ultra-low permeability reservoirs, like the development of Sulige gas field, needs to emancipate the mind.
"How to know ultra-low permeability reservoir? We should not only see its shortcomings such as dense reservoir, low abundance, low pressure and low single well output, but also see its advantages such as large resource scale, superposition of multi-layer systems, strong stable production capacity, suitability for water drive development and good crude oil quality. Seeing the negative side is seeking truth from facts, and seeing the positive side requires emancipating the mind. The development of ultra-low permeability reservoirs is a process of seeking truth from facts and a process of always emancipating the mind. " Shen, director of the ultra-low permeability reservoir development department of Changqing Oilfield, told the reporter.
The third project department of ultra-low permeability reservoir development is an oil production unit transformed from the third oil production technology service department of Changqing Petroleum Exploration Bureau in August 2008. The third project department of ultra-low permeability reservoir did not have its own block and proved reserves 1 ton before reconstruction. On August 28th, 2008, 662 square kilometers of Baoziwan South was handed over to the Project Department by No.5 Oil Production Plant. "The Jurassic reservoir that was originally developed for more than 30 years has dried up. In this ultra-low permeability reservoir, the daily oil output of several oil outlets adds up to a tanker and is taken away. At that time, standing on Liu Yuyuan, at first glance, it was false to say that he was not depressed. " Yang Xuefeng, deputy chief engineer of the third project department of ultra-low permeability reservoir, said, "But as long as there is a production point, there is hope. Since 2009, our project department has started from these oil production points, and the evaluation and production construction have been carried out simultaneously. At present, three reservoirs, Chang X, Chang Y and Chang Z, have been combined and connected, and the reserve scale of more than 654.38 billion tons has been controlled. In June this year, 5438+ 10, the daily output of crude oil in this block reached 1200 tons. "
This is true of the third project department of ultra-low permeability reservoir, the first, second and fourth project departments of ultra-low permeability reservoir, and the ultra-low permeability project teams of various oil production plants. When they took over ultra-low permeability blocks, most of them didn't even have proven reserves of 1 ton. But today, more than two years later, the tertiary reserves of these units have reached 654.38 billion tons, with an annual output of 4.3 million tons.
Straightened by numbers
Before June 2008, there was no discovery in Luo 228 well area of Huanjiang Oilfield. At the beginning of 2009, drilling in Well Luo 73 found a long Z oil layer with a thickness of 18m, but the permeability was only 0.3 Darcy and the porosity was only 0.9%. Can such a reservoir achieve effective development?
After the start of ultra-low permeability reservoir development, four ultra-low permeability reservoir project departments and ultra-low permeability reservoir project teams of oil production plants are faced with blocks that are difficult to get involved in normal production and construction and have been neglected for many years. When they took over these blocks, the same question puzzled them: Can such reservoirs be effectively developed?
"Confidence comes from practice and from technological innovation." Wu Xiaoming, head of the ultra-low permeability project team of No.7 Oil Production Plant, said: "Well Luo 73 achieved a daily output of pure oil 14 tons through effective reservoir reconstruction, and broke through Well Luo 228 in one fell swoop. Subsequently, exploration and development are integrated, and evaluation wells and skeleton wells are put together. After half a year, 300,000 tons of production and construction blocks will be implemented. Since 20 10, the daily production of single wells in this block has been greatly increased to 18 tons, and the daily production of single wells has stabilized at 2.7 tons. The lingering question mark in my heart has become confidence and courage. "
Technological innovation is embodied in every block and every link of ultra-low permeability reservoir development, and the background of technological innovation is the innovation of development concept. Regarding water injection, besides "moderate", there is also "advance". Ultra-low permeability reservoir has low pressure, low abundance, no natural productivity, no fracturing and no water injection, and the productivity of the oil well drops rapidly after it is put into production. Therefore, advanced water injection is an effective means to improve single well production, but everything should be properly controlled. Through advanced water injection, several development wells in the south area of Baoziwan actually achieved the effect of self-injection. This was originally a good thing, but the main leaders of the oilfield were keenly aware of the potential problems: on the one hand, the single well production did improve, but on the other hand, it also showed that the water injection intensity was too high, which might cause water series and flooding, and ultimately affect the stable production and enhanced oil recovery, so they proposed that "for ultra-low permeability reservoirs, the single well production should not be regarded as a hero". Therefore, the advanced water injection technology policy has been further optimized, creating conditions for achieving stable production and improving oil recovery.
The development of ultra-low permeability reservoirs has formed five technical series with 15 characteristic technologies, each of which is the result and starting point of innovation. Fracturing is the key of reservoir reconstruction technology in ultra-low permeability reservoirs. Changqing Oilfield grew up in low permeability. However, fracturing in different blocks, wells and reservoirs is a process of re-innovation. The second project department of ultra-low permeability reservoir, which is responsible for the development of Huaqing Oilfield, initially had only a single well 1.5 tons. Through the implementation of all-ceramsite multi-stage fracturing, especially hydraulic jet fracturing, the single well production has increased by 20% ~ 25%.
In the past, people thought that ultra-low permeability reservoirs were not suitable for horizontal well development. Is it true?/You don't say. Ran Xinquan, general manager of Changqing Oilfield Company, put forward the view that "this low permeability is not that low permeability", which shows that the understanding of low permeability oil and gas reservoirs is a continuous and in-depth process, and we should not only dare to explore and challenge, but also actively understand and overcome low permeability. Under this background, the horizontal well development test of ultra-low permeability reservoir is started again. In 20 10, Huaqing oilfield implemented 5 horizontal wells/kloc-0, and the drilling and fracturing were greatly improved compared with before. On June 5438+ 10, when the reporter interviewed, the output of all the five wells that had been put into production for three months was stable at about 8 tons, which was nearly four times that of the vertical wells in the same area.
"Of course, these five wells alone do not mean that the horizontal well development technology in ultra-low permeability reservoirs has been successful, but it shows us the dawn. The process of technological innovation is a difficult exploration process. Every small progress has made us more confident and determined to build Huaqing Oilfield into a million-ton oilfield. " Pei Runyou, Party Secretary of the Second Project Department of Ultra-low Permeability Reservoir, told the reporter.
Continuous technological innovation will not only increase the output of a single well, but also reduce the development cost. Three-phase separator, heating furnace and booster pump are skid-mounted to replace the original three kinds of equipment, thus reducing the land occupation. Single well mining, associated gas has no recovery value, all of which are vented and burned. However, the large well cluster wells composed of 9 to 15 production wells have large and stable associated gas volume and are used for power generation. The generated electricity drives the pumping unit, saving the development cost and reducing the waste of resources. The original pumping unit power was 15 kW to 20 kW, which was gradually increased, and now it is reduced to 7.5 kW. Digitalization is the biggest technological innovation in the development of Changqing ultra-low permeability oil and gas reservoir. Through digitalization, the comprehensive employment of single well has been reduced from 2.6 1 to 0.86. The number of employees with a capacity of one million tons decreased from 1.600 to 1.000.
Numbers are boring, but behind them are vivid and fiery technological innovations. In the development of ultra-low permeability reservoirs, Changqing people are faced with low permeability, but their ideas are highly permeable, and the inspiration of innovation permeates every detail from the development concept.