(Institute of Coalbed Methane and Reservoir Engineering, Drilling Engineering Technology Research Institute of China Petroleum and Natural Gas Corporation, Beijing 100 195)
Abstract: CBM horizontal well group consists of one or several horizontal wells connected with a cave vertical well, which is used for gas production. According to the characteristics of coalbed methane horizontal wells, a set of long-distance needle drilling equipment is developed to guide the communication between horizontal wells and vertical wells. Its theoretical basis is the rotating magnetic field positioning method, which monitors the relative position between the drill bit and the cave by measuring the rotating magnetic field in real time. The trajectory measurement and control model, equipment characteristics and composition of long-distance needle threading technology are discussed in detail. Through field application, the needle threading equipment can accurately locate and guide within 60m distance, and the specific technical indicators have reached the international advanced level.
Key words: rotating magnetic field of coalbed methane horizontal well, long-distance needle penetration between two wells
Remote intersection technology between horizontal wells and vertical wells in coalbed methane development
Tanaka Lanshen Chen Rui Qiao Lei
(Drilling Engineering Research Institute of China Petroleum and Natural Gas Corporation, Beijing 100 195)
Abstract: According to the particularity of low pressure, permeability and water cut of coalbed methane in China, an additional vertical well is generally needed for coalbed methane horizontal wells, which are connected with multi-branch horizontal wells for sucker rod pumps to enter drainage and gas production. Rotating magnetic field positioning technology is introduced into the docking process between horizontal wells and vertical wells to improve the success rate of docking. The relative position between the borehole and the cave is modified by real-time magnetic field measurement to guide the connection of the two walls. In this paper, the rotating magnetic field model and remote control needle technology are discussed in depth. The measurement method of the distance and position deviation between the drill bit and the cave is established. Specially developed the remote rendezvous equipment. The field application proves that the theory and technology are feasible. The equipment can find the signal within 60 meters.
Keywords: coalbed methane; Horizontal well; Rotating magnetic field; Wells remote needle
About the author: Tian Zhonglan, male, deputy director and senior engineer of CBM Research Institute of Drilling Engineering Technology Research Institute of China Petroleum and Natural Gas Group Company, mainly engaged in related research on long-distance needle piercing tools, coal seam borehole stability, reservoir protection and so on. Tel: 01052781885; Email: tianldri @ cnpc.com.cn.
1 Introduction
China is a country with large coal resources in the world, and the total coalbed methane resources are 36.81×10/2m3, which is basically equivalent to the conventional natural gas resources and ranks third in the world. Coalbed methane reservoirs in China are generally characterized by low pressure, low permeability and low water content [1 2]. Considering enhanced oil recovery and economic benefits, horizontal wells and multi-branch horizontal wells are the best development methods [3]; Based on the particularity and extraction method of coalbed methane development above; Usually, the horizontal well of coalbed methane needs to be drilled with an additional vertical well, which should be connected with the horizontal well (as shown in figure 1) so as to run the screw pump and sucker rod pump for drainage and gas production. Long-distance needle piercing technology and equipment is one of the key technologies to realize long-distance accurate communication between two wells, and it is also a necessary technology for drilling multi-branch/U-shaped horizontal wells of coalbed methane.
Figure 1 Schematic diagram of horizontal well exploitation of coalbed methane
At present, the conventional borehole trajectory control technology mainly uses wireless inclinometer while drilling (MWD) to locate and control the drill bit underground, but the drilling technology of coalbed methane horizontal wells requires communication between horizontal wells and vertical wells, so it puts forward higher requirements for borehole trajectory measurement and control [4]. Because the target area at the vertical shaft of the cave is a long and narrow rectangular frame of 0.5m× (4 ~ 8) m, MWD measurement method is far from meeting the requirements of trajectory measurement and control of horizontal wells of coalbed methane. In order to meet the needs of large-scale and commercial exploitation of coalbed methane in China, China Petroleum Group organized key research projects based on the national major special project "Large-scale oil and gas fields and coalbed methane development" during the 11th Five-Year Plan period. The project team has successfully developed a 43/4 long-distance needle threading tool after more than three years of 100 experiments, forming a set of long-distance needle threading measurement and control technology, which can capture signals at a distance of 70m and accurately locate and guide operations at a distance of 60m. The whole set of equipment has high reliability and can meet the requirements of industrial application.
Fig. 2 Measurement parameters and structural characteristics of traditional MWD nipple.
Measurement and control model of long-distance needle threading trajectory
The goal of trajectory measurement and control of coalbed methane horizontal wells is to gradually narrow the uncertain ellipse range of the relative position between cave wells and horizontal wells. By introducing the rotating magnetic field, the distance and azimuth deviation between the horizontal well bit and the cave well can be directly measured (as shown in Figure 3). When the relative position of the two wells is clear, the trajectory of the horizontal well can be adjusted, and finally the vertical hole of the karst cave can be drilled.
The calculation formula of the distance and azimuth deviation between the horizontal well bit and the cave well is as follows [5,6]:
Fig. 3 borehole trajectory measurement and control model of connected well groups
Fig. 4 schematic diagram of the distance between the drill bit and the cave and the deviation of drilling angle.
Technical progress of coalbed methane in China: 20 1 1 Proceedings of the symposium on coalbed methane.
Where: r and θ are the distance (m) and azimuth (degree) between the cave and the horizontal well bit (Figure 4); K is the proportional coefficient, and HX, HY and HZ are the three components (nt) of the magnetic field signal.
Development of 3 4-3/4 long-distance needle threading equipment
Fig. 5 structural schematic diagram of long-distance needle threading system
Long-distance needle threading positioning equipment (MTSI) is mainly composed of magnetic sub, magnetic array sensor, measuring circuit sub, ground power supply and industrial computer, as shown in Figures 5 and 6. The main body of the magnetic sub is made of nonmagnetic materials, and some strong magnetic cylinders are embedded in the sub, which is mainly used to form a "rotating magnetic field" when the drill string rotates, with the same frequency as the drill string, about 2 ~ 5hz. Probe tubes are mainly used to detect rotating magnetic field signals (Hx, Hy, Hz), collect and amplify the measured signals, and transmit them to the wellhead of cave wells through cables. Finally, the distance and direction deviation between the drill bit and the cave are calculated by the established magnetic field measurement model. The design detection range of MTS-I long-distance needle piercing tool is that the azimuth measurement error of 70m system is less than 0.4 and the distance measurement error is less than 5%. It can realize the short-distance measurement function within 5m, and the signal is not saturated and distorted.
Fig. 6 Module diagram of long-distance needle threading equipment unit
Fig. 7 Borehole Trajectory of Well Group DSFC-03
4 field application
MTS-I long-distance needle piercing tool has been used in well DSFC-03 in Binxian block of Ordos Basin. Well DFS-C03 is a 880m U-shaped well (as shown in Figure 7). At the depth of 12 13m, the magnetic field signal begins to appear. Through data collection and calculation, the azimuth deviation is 4.48 degrees, and the calculated distance is 69.72 meters: according to the above calculation results, in the well depth1213 ~1219 meters and1222 ~10. Until the deviation of the specified position at the well depth/kloc -0/235m becomes-0. Considering that the azimuth angle of inclination is less than 1 degree, composite drilling was carried out at the interval of1252.6 ~ 126 1.4m, and at126/4m. However, as the drill bit approaches the cave, the azimuth deviation angle will increase sharply, so the azimuth distortion operation will continue until the two wells are connected. Well depth 1284.2m, azimuth angle of inclination is stable at 2.63, error radius is 0. 16m, cave diameter is 0.5m: well depth 1284.2m, riser pressure suddenly drops, and mud returns, indicating that two wells are connected. See table 1 and figure 8 for the detailed connectivity measurement process.
Table 1 DSFC-03 Well Construction Process
Fig. 8 Site Construction Positioning Map
5 conclusion
(1) The research on the measurement and control model of needle threading trajectory is the basis of developing MTSI remote needle threading equipment. Based on the characteristics of rotating magnetic field generated by permanent magnet nipple and the drilling technology of coalbed methane horizontal well, the measurement model of distance and angle deviation between drill bit and cave is established.
(2) The magnetic field and gravity field of the MTSI needle piercing system are stable, and the data uploading and ground acquisition are fast and accurate; The signal can be captured at a distance of 70 meters, and the precise positioning and guidance operation can be carried out at a distance of 60 meters. The specific technical indicators have reached the international advanced level.
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