The Past and Present Life of MWD in Directional Drilling

Original Title: [Dry Goods Super Long Article] The Past and Present Life of MWD in Directional Drilling 1 Basic concepts 1. What is MWD instrument? MWD is the abbreviation of Measurement While Drilling. MWD instrument is an important member of the whole measuring instrument family. 2. What does the measuring instrument measure? The data obtained by the measuring instrument are the well deviation, azimuth and tool face of the instrument near the current downhole bit. What do these parameters mean? For example, these data can now be measured by ordinary mobile phones: A. Well deviation (horizontal and vertical angle) is equivalent to measuring the horizontal and vertical state of the mobile phone, and the horizontal or vertical screen will be given on the mobile phone. B. The direction (north, south, east and west) is equivalent to the compass of the mobile phone. C. The tool surface of the instrument (how to turn the head up, down, left and right) is equivalent to some "720-degree panoramic websites" of the mobile phone, and the scene picture can be updated with the rotation of the mobile phone. Expand the full text Measuring instrument integrates well deviation, azimuth, tool face and other measurements, but at the beginning of the invention of this kind of instrument more than 100 years ago, it mainly focused on well deviation data, so many people in China's petroleum circle still call it "inclinometer". 3. Why measure? Drilling is like walking, there must be a turn to reach the end, walking with eyes open to observe which intersection turns. Drilling also needs to control the drill bit to drill to the target point, and the measuring instrument is the so-called eye. Tell me where it is and where the target is. As an example in the figure below, a directional well needs to meander several kilometers underground to reach the target point of the oil layer under the guidance of the survey instrument. 4. What is measurement while drilling? The meaning of while drilling is relative to the traditional stop drilling. It is different from the wireline logging instrument or other instruments to obtain data at the cost of "stopping drilling" and then running in the measuring instrument. The method of stopping drilling at intervals is equivalent to walking a few steps with your eyes closed, stopping and opening your eyes to see where it is. If there is drilling technology, we can get real-time downhole data and know the specific location when drilling. It's like walking with your eyes open. 5. Why measure while drilling? A. First of all, it will take time and money to stop drilling. Once the drilling is stopped for measurement, it will take at least 4-6 hours, and more than 8-10 hours. If it is operated at sea, this period of operation may cost hundreds of thousands to millions of dollars per day. B. Pure blind drilling without the guidance of measurement data may lead to deviation from the target point, resulting in borehole collision and other risks. C. When measuring, the drill pipe is still, which causes the collapse of the well wall and the sticking of the drill pipe. Therefore, MWD overcomes the disadvantages of "stop drilling" measurement. The downhole data can be obtained in real time when drilling, and the specific location can be known. In addition to the high price, the measurement while drilling is better than the "stop drilling" measurement method in other aspects. 6. How to realize "real-time data" while drilling? The downhole instrument has no cable to connect with the surface instrument. That requires a coded transmitter for downhole instruments, a receiver at the surface, and a set of decoding programs. There are generally two ways to realize the coding transmitter of downhole tools. A. Drilling fluid pulse. It is equivalent to putting the hand in the water flow under the faucet,fastest dth hammer, twisting the knob of the faucet, and the impact pressure on the hand will change. The downhole instrument limits the flow of drilling fluid through an electronic mechanical switch and transmits data in a certain frequency sequence, and the ground sensor will sense the pressure change and demodulate the signal. And B, wireless electromagnetic pulse, wherein that downhole instrument transmit a radio signal pulse. There is a wireless receiver on the ground to receive the wireless signal. MWD, a modern measurement while drilling instrument, is evolved step by step from the predecessors of "stop drilling measurement". Let's straighten out MWD and its predecessors. 2 The History of the Family of Measuring Instruments At the very beginning, the measuring instrument may only be used to measure where the well is finally drilled. If there is no instrument that can control the trajectory, it can only be known but not controlled, and its role is limited. Therefore, the development of measuring instruments is closely related to the development of trajectory oriented control instruments. The more advanced the directional instrument is, the stronger the controllability is,dhd drill bit, and the higher the requirements for data quality including measurement frequency and accuracy are, which objectively promotes the development of measurement instruments, so that the oilfield can obtain greater productivity in a certain space and time, and improve the efficiency of the oilfield industry. 1. Chemical acid bottle method or physical firing pin method measuring instrument The acid bottle method was invented abroad at the beginning of the 20th century and was basically eliminated internationally in the 1940s. It was widely used in China in the 1950s and 1960s. In China, after the drilling is stopped, an instrument string containing a small bottle of hydrofluoric acid liquid is lowered from the drill pipe by a wire rope. When the instrument touches the valve seat at the bottom of the drill pipe, it triggers a physical mechanism or timer. If there is a deviation, the liquid level of hydrofluoric acid will corrode on the vial, forming marks of different heights in different directions. After pulling the instrument string out of the wellhead, observing the corrosion marks on the liquid level, the downhole deviation and azimuth instrument surface can be obtained. This method has been eliminated with the development of science and technology because of its high failure rate and low accuracy due to chemical and physical reasons. At present, it is almost invisible in textbooks. There is also a physical firing pin type, which leaves a physical impact mark on the compass compass after the timer is triggered. This has also been replaced with the development of science and technology. 2. Photographic measuring instrument This method was invented abroad in the early 20th century and widely used in the early 1920s and 1930s. It began to be studied in the 1970s and 1980s in China, and began to be imported and applied in the 1980s and 1990s. When there is a "memory" of camera film that can be recorded, there is no need to use the permanent marking method of acid bottle corrosion scale. In this way, a small instrument with compass compass and heavy hammer is connected to a timing camera. A steel wire is lowered into the drill pipe that stops drilling. The battery opens the shutter grating of the camera to expose and image. Then the instrument is taken out to the ground and the film observation results are developed. The general instrument cannot rotate the film, and only one photo can be taken for each construction. Most of the commercial chemical formulas and photographic models are also "Single Shot", because each construction can only measure the data once, and take it out to the ground to see the results. This is different from the concept of "Multi Shot", which can measure multiple data in one construction. Photographic inclinometers have been widely used in land drilling teams in recent years, and in the South China Sea, they were basically eliminated around 2014. 3. Electronic Multi Shot As the name implies, down the hole bit ,dth hammer bit, the multi-point inclinometer can measure multiple points in one construction when the drilling is stopped for measurement. With the development of wireline logging, the instrument has been gradually improved. It has been invented since the beginning of the 20th century and has been continuously improved and developed. When the whole industry entered the electronic age, the electronic multi-point inclinometer gradually matured. A. First of all, the cable replaces the wire rope. Because the cable can supply power, obtain data and control the instrument, the battery in the instrument is saved. In this way, the computer on the ground can send measurement commands to the downhole instrument through the cable at any time, and the on-site QC data can be measured, and the points with low quality can be re-measured immediately. Secondly, electronic components such as electronic gyroscopes, electronic gravimeters and electronic compasses have replaced physical weights and compasses; electronic memory has replaced camera film. And C, a depth sensor attached to the cable roller can measure the length of the cable and provide accurate depth calculation for the measuring point. This configuration is still widely used in the modern oilfield industry. The wireline logging department and the directional well department are generally responsible for these operations, providing wireline winches and measuring instruments. 4. Input MWD Input MWD is an epoch-making product, which realizes real-time measurement data transmission. One of the leading technologists of the instrument should be Anon of Schlumberger, who published a large number of papers on the development and improvement of MWD from 1981 to 1984. Before tripping in, put a section of throw-in MWD instrument on the valve seat in the drill collar, and then enter the well for normal drilling. During the drilling process, the instrument transmits real-time measurement data to the surface. Because there is no cable to transmit data, modulation transmitters are designed into instruments to transmit data to the surface through pressure changes, while pressure sensors are installed on the surface to demodulate the signals transmitted underground and turn them into data that can be read by human beings. Of course, when there was no cable power, the battery was redesigned into the instrument. This kind of input instrument is relatively easy to maintain and low cost for modern industry. It is widely used in land oilfields. Some products of foreign enterprises have mature products in the 1990s. Domestic research and development began in the late 1990s. 5. Integrated MWD The throw-in MWD combined with the drill collar becomes an integrated MWD. This device is an upgrade to the drop-in MWD. The driving force is the demand for LWD and RSS matching with MWD. What are these needs? A. Addition of power generation turbine modules or upgrade of larger batteries. MWD, as the pioneer of downhole equipment and the necessary equipment for basic data acquisition, shall be provided to other equipment LWD and RSS power. B. Generation of communication interfaces of other downhole instruments, and upgrade of hardware and software required to communicate with other downhole equipment. C. Integration of more sensors. All these require the MWD to have a larger volume, and the large volume is contradictory to the small internal space of the drill collar, so the modules of the MWD are fixed in special drill collars in different shapes to save space. This is the integrated MWD. As shown in the figure, Schlumberger has been working on various MWDs of input and integration since the early 1980s. And it's still evolving. Integrated MWD is now the mainstream measuring instrument for foreign enterprises. Its disadvantages are high integration, complex maintenance and relatively high cost. The leading products in the world include TeleScope of Schlumberger, OnTrack of Baker Hughes, and then many foreign companies such as Halliburton, Weatherford and International Scientific Drilling SDI in the second line. The leading domestic enterprises are also involved. Only the instruments produced by COSL around 2015 are still in the stage of experimental improvement; PetroChina had a similar scientific research problem around 2012, but recently it seems that no sound can be heard. 6. Future integrated/decentralized products? As sensors become smaller and more diverse, future products may integrate MWD, various LWDs, and rotary steering to a high degree. If you want to know more about the inside of the wellbore. It is necessary to decentralize the attachment of instruments at various positions of several kilometers of drill pipe. However, the development of this technology needs to be promoted by the progress of intelligent drill pipes of international foreign enterprises. Intelligent drill pipes are still being developed and tested, so it is difficult to predict the commercialization time of future measuring instrument products. Among the above inclinometers, the acid bottle type and mechanical type have been eliminated and will not be included in the future discussion. Other generations of products are used in the oilfield. The accuracy of required data is one aspect of instrument selection. The deviation accuracy of each generation of instrument is about 0.1 degree, and the azimuth accuracy is about 1 degree. Can meet that requirement of general well conditions. The cost consideration is mainly the rental price and reliability of the instrument. The price of different instruments may vary by tens of times. If the instrument fails, the potential cost of pulling out and replacing the instrument can be estimated, but the indirect loss of wellbore instability is incalculable. The more complex the well is, the greater the potential loss caused by instrument failure is, so the reliability of instrument is a very important factor. 3 Overview of China's Skew Instrument Market The key technologies of the mainstream measurement instruments in the world are in the hands of Schlumberger, Baker Hughes, Halliburton and Weatherford. Many small and medium-sized enterprises located in Europe and the United States also have leading or equal positions in some technologies. Domestic manufacturers of inclinometers are mainly oil service companies or R D and design institutes of directional well companies affiliated to domestic state-owned petroleum enterprises, while private enterprises are mainly companies with geological and mineral exploration design, space shuttle navigation or military background. As far as the use of inclinometers in China is concerned, single-point inclinometers are basically outdated products, and there may be a little market on land. Multi-point inclinometer technology has been relatively mature in China, and it is the main instrument used in onshore oilfields, which has been basically localized, and rarely used offshore. Input-type MWD is active on land and a small number of offshore platforms in China. The instruments mainly used in China mainly come from two companies: one is the Solar series instruments of Sperry Sun of Halliburton, which were sold to COSL more than 10 years ago. Simple maintenance can be carried out in COSL, and the overhaul still needs to be returned to Halliburton's overseas base; Second, Schlumberger made a joint venture with Jindi Weiye, a domestic private enterprise, six years ago, and transferred part of SlimPluse to Jindi Weiye in a certain form, and then seized the low-end market on land. These foreign manufacturers have taken the lead in technology and quality. Although many domestic input instruments also have part of the market in the land drilling team, the overall reliability is not high. Domestic products have basically not entered the offshore drilling market. Integrated MWD is mainly used in a small number of onshore drilling fleets and most offshore platforms, mainly instruments such as Schlumberger's TeleScope and Baker Hughes' OnTrack, which enter the Chinese market through subcontracting by COSL or directly signing contracts with CNOOC. Halliburton and Weatherford also have a small number of markets. At present, Welleader, a product of COSL, has also been tested around 2015, but has not yet been put into the market on a large scale. The main problems of domestic instruments are the precision of mechanical part, the temperature and oil resistance of rubber seal ring, the shock resistance of electronic part and the adaptability of temperature deviation. In order to enter the international market of MWD and other fields, it is difficult for domestic small and medium-sized enterprises to complete alone,Borehole Drill Bits, which requires the state to set up projects and concentrate technology and funds to tackle key problems. Perhaps in this case, in the next 10 years, domestic products can achieve curve overtaking and occupy the international leading level. Welcome to the official account: Petroleum Link Return to Sohu to see more Responsible Editor:. wt-dthtools.com