"Smell" the seabed "Xuanji" of drilling oil

Demystifying the "crown jewel" of oil drilling technology

Waves churn, ebb and flow... At the northern tip of the eastern part of China's continent, the Bohai Sea is like a sloping gourd, surrounded by land.

As the only inland sea in China, it not only has abundant and high-quality fishery, sea salt, shipping and other resources, but also rich oil and gas resources.

After more than 50 years of exploration and development, today's Bohai Oilfield is the largest offshore oilfield in China and the largest crude oil production base in China. Data show that in the past decade, more than <>% of the <> million-ton large oil fields discovered in China are in the Bohai Sea. It is like a huge "oil basin" and has made important contributions to ensuring national energy security.

The reporter learned that the current daily output of crude oil in Bohai Oilfield has historically exceeded the 9,30-ton mark, equivalent to one-sixth of the country's crude oil daily output, which is the best daily output level in the history of Bohai Oilfield. From the initial daily output of more than 9 tons, it has now exceeded <>,<> tons, thanks to the continuous innovation of offshore oil and gas exploration and development technology. The rotary steered drilling and logging while drilling technology, known as "Xuanji", is one of them.

The reporter recently came to the Bohai oil field to explore the secret of the "Xuanji" on the seabed.

Seabed "diamond diamond", the "key" to open complex oil and gas reservoirs

Exceeded 1000,100 wells, with a total drilling advance of more than <> million meters

Recently, with the successful completion of the drilling operation of a directional well in Bohai Oilfield, the "Xuanji" technology independently developed by CNOOC has successfully exceeded 1000,100 well operations and <> million meters of total drilling footage, marking a milestone in China's high-end oil and gas drilling technology, and its comprehensive technical capabilities have officially entered the world's top ranks.

"Xuanji", that is, rotary guided drilling and logging while drilling. This is a revolutionary and disruptive technological breakthrough in the field of oil and gas exploration and development in China, representing the highest level of drilling technology development in the world today, and is known as the "crown jewel" of oil drilling technology.

"It can accurately control the drill bits in the rock formation several kilometers underground to 'target' the oil and gas, 'look' the boundary drill, and even accurately travel thousands of meters in a thin oil layer only 1 meter thick, so as to 'eat and squeeze clean' the oil and gas treasures." As a "user" of this technology, Wang Yunhai, project manager of drilling and completion in Qinhuangdao/Bozhong Regional Drilling and Completion Center of CNOOC Tianjin Branch, was deeply impressed.

According to him, there are many links in oil and gas resources from exploration and development to delivery to users, and drilling can be called the "throat" link of the entire chain.

The reporter learned that the first step in oil and gas exploration and development is "exploration". Simply put, it is to find oil and gas resources. Geologists and explorers use professional equipment to do "nuclear magnetic resonance" on the formation to determine the approximate area of oil and gas existence.

Then comes the drilling process. "This is critical if you want to make the oil and gas resources really 'for my use'." Wang Yunhai told reporters that drilling is to drill through the rock layer through a hard drill bit to reach the location of the reservoir, "In layman's terms, it is to build a tunnel from the oil and gas layer to the surface, so that the oil and gas reservoir can be exploited through this tunnel." ”

However, the tunnel was not an easy task.

"You have to have a 'diamond diamond', this diamond must not only ensure that it can hit the oil and gas layer, but also ensure that it can be hit accurately and successfully, otherwise it will affect many subsequent operations." Wang Yunhai said that any failure in the drilling process will zero out all efforts, especially at sea.

Unlike what we imagined, abundant oil and gas resources are not quietly gathered in large "oil basins" on the seabed, but scattered in the pores of different strata on the seabed, which is extremely difficult to exploit. This characteristic is particularly prominent in the Bohai oilfield.

Industry insiders often use "broken porcelain plate" to describe the distribution of oil and gas resources in the Bohai oilfield. "The structure of the Bohai Bay Basin is finely shattered, like a porcelain plate shattered, and it has been trampled on several times, and there is almost no complete place." Wang Yunhai told reporters that with the deepening of oil and gas exploration and development, more and more oil and gas reservoirs in the Bohai Sea that need to be developed urgently are facing the situation of "edge, small, fine and broken", the thickness is getting thinner and thinner, and the development is becoming more and more difficult.

At the same time, limited by the technical characteristics and economic requirements of the inflexible movement of offshore platforms, offshore oil production platforms usually the size of half a football field need to cover the surrounding area of submarine reservoirs tens of thousands of times higher than their own area and thousands of meters deep. Sometimes, it is even necessary to drill nearly 100 wells on an oil production platform, which is often called a cluster well, and the wellbore trajectories are crisscrossed, like a huge root system of vegetation, expanding from top to bottom, and the bottom end of each branch must be accurately inserted into the oil and gas reservoir in order to continuously transport oil and gas to the platform wellhead.

This means that the tunnel is not straight up and down, it can be inclined, horizontal, or even roundabout.

How does this bend go around? It requires a technology, which must have both the "hands and feet" like the direction adjustment function, and the "eyes" and "nose" like the environmental perception function, with thousands of meters of drill pipe, avoid adjacent well casing, drill through hard rock, and plunge into the oil layer with a graceful posture, like a "gluttonous snake", going through and strung up the oil and gas reservoirs, "eating dry and pressing".

"Xuanji" is one such technology.

Aim at oil and gas and control the wellbore trajectory freely

The recovery rate of a single well can be increased by a factor of 2 to 3, saving nearly half of the operating time

At about 3 o'clock in the morning of March 14, in the dark night before dawn, a drilling platform in the Bozhong Sea was brightly lit -

The first batch of development wells in Bozhong 29-6 oilfield were drilled to the target layer according to the pre-designed direction and trajectory, and "Xuanji" successfully completed the horizontal well drilling task again. Tian Qingpu, senior directional well engineer of Tanggu Operation Company (hereinafter referred to as CNOOC Oil Service Technology Tanggu), who was in charge of the drilling task, stayed up almost all night, waiting for this moment.

At the same time, in Tianjin Binhai New Area, about 200 kilometers away from the offshore drilling platform, Bai Xuelong, a senior directional well engineer at CNOOC Oil Service Technology Tanggu, also received news from the offshore operation platform that the drilling had been completed.

"After the completion of the follow-up completion operation, nearly 3000,29 meters of oil and gas resources on the seabed will be continuously exploited through the channel opened by 'Xuanji'." Bai Xuelong told reporters that the large-scale application of the "Xuanji" technology independently developed by CNOOC in the Bozhong 6-<> oilfield project has greatly reduced the cost of drilling tools.

It is understood that the project faces a series of difficulties such as complex borehole trajectory of directional wells, severe risk of shallow collision prevention of large-scale cluster wells, arduous tasks of speeding up and improving efficiency, and no historical data of developed wells in the block. The development well, which has just been drilled, is a horizontal well, and drilling is extremely difficult. With conventional guided drilling tools, it takes 3 days to complete a drilling operation of the same difficulty, while with Xuanji technology, it only takes 2 days, saving one day in drilling time.

Bai Xuelong said that operating wells for oil and gas resource development are generally divided into two categories. One type is straight wells, that is, shafts that go straight up and down. The other type is directional well, the well body can be drilled to the target layer along the pre-designed direction and trajectory, generally refers to oblique drilling and horizontal drilling, that is, the drilling trajectory is not straight up and down, but there is a certain angle with the vertical direction, when this angle is less than 55 degrees, it is called a conventional directional well; When the angle is between 55 degrees and 86 degrees, it is called a large slope directional well; When this angle is greater than 86 degrees, or even reaches 90 degrees and drilled horizontally, it is called a horizontal well.

"Drilling of difficult wells such as horizontal wells and large-slope wells has always been a problem in the industry, and 'Xuanji' is the magic weapon to solve these problems." Shang Jie, the technical leader of "Xuanjie" and chief engineer of CNOOC, said.

The key to this is the "rotary guide", which allows accurate control of the direction of drilling even when the drill bit is rotating at high speeds.

"If a traditional guide drill is compared to a 'classic car', then the rotary guide is equivalent to a 'supercar'." Bai Kezong, deputy manager of CNOOC Oil Technology Tanggu, told reporters that there is no "navigation" and no "automatic driving" in the era of "classic cars", although it can meet most of the travel needs, but when walking on a winding and complex "track", it still needs to drive faster, have stronger "turning" ability, "turn" accuracy and more intelligent "supercar". It looks and runs, runs and looks, finds the reservoir, drills into the reservoir, finds this one and goes to the next one, so as to string together as many oil and gas reservoirs as possible.

Since its birth in the 20s of the 90th century, rotary guided drilling technology has been monopolized by international oilfield service companies for more than 20 years because it spans more than 1000 disciplines, involves more than 20,10 high-end processes, and has millions of lines of control code. Faced with the high service fee of 7 billion yuan per year, the technical blockade of complete encryption and the monopoly of products that are only rented but not sold, CNOOC successfully developed the "Xuanji" drilling and logging system and realized offshore operations in 2014 after seven years of technical research, making China the second country in the world to have this technology. This technology can increase the range of controllable oil and gas reservoirs by 4-5 times, increase the recovery rate of a single well by 2-3 times, and save 30%-50% of operation time.

"Since its first commercial application in 2014, Xuanji technology has undergone tens of thousands of reliability verification, structural optimization and iterative upgrade processes, and solved hundreds of technical problems. Up to now, it has obtained nearly 92 national patents, and the success rate of the key operation indicator - one-time well entry has reached 1.<>%, reaching the world-class level. Shang Jie introduced.

"Xuanji has a maximum inclination capacity of more than 60°/100m, which can realize the free and precise control of three-dimensional complex borehole trajectories." Bai Xuelong told reporters that in other words, every 100 meters of drilling can guide 60 degrees. In this way, in horizontal development well operations, the length of the inclined well section can be reduced by more than half, contributing to longer reservoir sections. When drilling complex formations, the drilling trajectory can be adjusted more quickly, the reservoir drilling rate can be improved, and the operation safety can be guaranteed, while achieving the lowest cost and fastest speed to complete the drilling.

See the boundary clearly and obtain formation information in real time

It can invert the geological structure around the whole well and has a "5G" level transmission rate

On another offshore platform not far from the Bozhong 29-6 project, Xuanji is drilling on the seabed. At the same time, the staff on the platform obtained the strata information of the seafloor in real time through the ground system software.

"This is where the logging system is at play." Ma Chunbin, senior logging engineer at CNOOC Oil Technology Tanggu, told reporters that an important prerequisite for accurate judgment and control of drilling direction is to have a good understanding of the underground geological structure. Especially in complex cluster wells, the wellbore trajectories crisscross, like a huge root system with vegetation, the initial spacing between adjacent wells is even less than two meters, and once a "collision" occurs during the drilling process, it is very likely that a blowout accident may occur, causing billions of direct property losses and immeasurable environmental pollution.

"Xuanjie" has such a pair of "eyes" that can "see" the surrounding environment clearly. According to reports, its detection capability can reach a maximum radial depth of 6.8 meters, which supports 360° real-time inversion of geological structure around the whole well and realizes visualized geology-oriented drilling. "In other words, while drilling wells, it can see the surrounding conditions within 6.8 meters, such as the surrounding geological structure, whether there are oil and gas resources or other wellbores." Bai Kezong told reporters that this electromagnetic wave "radar perspective" capability can lock the completion drilling hole in the best position of the reservoir, greatly increasing the upper limit production capacity and stable production time of oil and gas wells.

Traditional logging tools can only log two parameters, oblique and azimuth, and cannot obtain more parameters for analysis. "Figuratively speaking, just like when we drive without navigation, between the start and the end, we can only drive according to the fixed route determined at the beginning, and we can neither know in advance whether there are special circumstances such as traffic jams and road construction ahead, nor can we make corresponding adjustments in time." Wang Yunhai said.

Xuanji has a complete acoustic core logging function while drilling, which can realize the measurement while drilling of the "four lines" of natural gamma, resistivity, neutron porosity and lithological density, as well as high-end technologies such as quadrupole acoustic wave and formation manometry, which can perceive the surrounding information more comprehensively and widely meet the requirements of logging while drilling for various tasks from complex geological guidance to formation evaluation while drilling.

However, thousands of meters underground, it will not obediently tell you what it sees and where it is going next. "This requires our platform operators and 'Xuanjie' to bring the 'walkie-talkie', what it sees, tell us in real time; after we analyze and judge, we want it to go where it goes, and also issue corresponding instructions in time." Bai Kezong explained that through mud pulses and ground diversion, they established two-way communication between ground personnel and Xuanjie, "Once a special situation is found, it can be fed back to the operator in time, so as to create an optimized, time-saving and smoothest route." ”

Its mud remote transmission rate is up to 20bps, and it can support real-time upload of 100 measurement curves at high drilling speeds of 30 m/h. This industry's "5G" level transmission rate provides more measurement information for real-time identification of complex geological conditions, which in turn facilitates correct and rapid drilling operation decisions.

"Simply put, it is faster and better than conventional logging." Shang Jie said that with the reliable performance and wide practicality of Xuanjie, oil and gas reservoirs can be accurately identified and evaluated in a single well, greatly reducing exploration and development costs.

The reporter learned that in addition to the Bohai oilfield, "Xuanji" technology has been widely used in major oilfields such as the East China Sea, the South China Sea, the Yellow Sea, Xinjiang, Liaoning, Shanxi, as well as Indonesia, Iraq and other countries along the "Belt and Road", contributing Chinese wisdom and Chinese solutions to the world's oil and gas exploration and development. (Wang Zhen, reporter of China Discipline Inspection and Supervision News)