The earliest oil production method is open hole oil production or screen oil production. With the appearance of cementing technology, perforation oil recovery method has been developed. 1932, American LENEWELLS Company started bullet perforation; 1946, WELEX company began to use the ejection hole of shaped charge; 1949, mccullough Company started to engage in tubing conveying perforation (TCP), but it was not developed because the technology was not in place; 1953, Exxon and Si Long Becherley Company started tubing perforation, 6548+0949.
At present, the world-class perforation companies include Compac, Halliburton, Owen, Goex, Baker, Schlumberger and so on. The perforating equipment of these companies has the same characteristics: high product serialization, high processing precision, complete detection means, accurate and complete detection data, rapid technical update, high-density and multi-directional high-tech development, and little drilling cuttings pollution.
In China, before 1958, Soviet perforators were used. In the early 1960s, casing coupling with magnetic positioner was used for perforation positioning. In 1970s, perforation through tubing was widely used. In the mid-1980s, TCP technology of tubing conveying perforation was introduced, and it was gradually popularized and used in various oilfields after 1988.
With the continuous expansion of offshore exploration achievements, the focus of offshore oil exploration and development will further shift from exploration to development, and the number of oilfield development wells will increase year by year. However, most offshore oil fields to be developed belong to marginal oil fields. If imported equipment is used in development, many marginal oil fields cannot be developed because of high cost. In order to meet the demand of offshore oil and gas exploration and development wells for new series of perforating equipment, it is urgent to replace imported products with domestic perforating equipment, reduce the development cost, fill the gap of high-density perforation of domestic casing, promote the exploration and development process of offshore oil in China and develop new perforating equipment. Although China's perforating equipment products have made great achievements in small caliber and low density, compared with the international level, the overall level is still low and the processing accuracy is poor. In addition, the product series is not matched and the detection methods are not perfect, which can not fully meet the needs of offshore operations.
In order to further reduce the cost of offshore oil exploration and development, and speed up the localization process of perforating equipment, China Offshore Oil Corporation has developed the perforating guns for tubing conveying (TCP)-HY 1 14 and HY 159, and put these patented products with independent intellectual property rights into production as soon as possible.
(1) offshore perforation
1. Punch
The downhole operation that uses the energy of fire fighting equipment or other energy sources to open casing, cement sheath and stratum and communicate oil and gas flow channels is called perforation.
Perforation is an indispensable means in the process of exploration and development. After oil and gas reservoirs are discovered by drilling, logging and mud logging, casing must be set and cemented, and then perforation and oil testing must be carried out to determine whether this layer has exploitation value. For the development of production wells, completion and perforation should be carried out first, and then other oil production and water injection operations such as running production string, running pump and sand control can be carried out. In the process of oil and gas field development, if the development plan is adjusted, it is often necessary to fill holes to maintain the output of oil and gas fields.
With the development of perforation technology and oil production technology and the accumulation of exploration and development experience of major oil fields in China in recent twenty or thirty years, the understanding of the importance of perforation technology has been gradually improved, and perforation operation has been paid more and more attention. Therefore, perforation technology in China has developed rapidly in recent years and made great achievements.
2. Punching mode
At present, there are three widely used perforation methods at home and abroad: ① cable conveying perforation; ② tubing perforation; ③ Tubing perforation (TCP).
These three kinds of perforation belong to explosive shaped charge perforation, that is, the process of focused high-energy jet produced by inverted cone high-energy explosive penetrating casing and formation.
Recently, hydraulic perforation has made a new breakthrough in penetration depth, but it has not been widely used.
3. Perforation technology
Perforation technology includes positive pressure perforation and negative pressure perforation. According to different wellbore conditions, formation conditions and completion technology requirements, different perforation technologies are selected.
A. Positive pressure perforation: In order to successfully produce oil and gas in the formation, casing must be run after drilling, and cementing must be carried out between the casing and the formation, and then perforation should be made on the casing and cement sheath of the oil and gas interval to connect the oil and gas flow channels. Therefore, before perforation, there are two different pressure systems in the formation and casing. If the liquid column pressure in the casing is greater than the formation pressure, the well fluid will press to the formation after perforation, and the compaction and pestle of perforation will cause "secondary pollution" to the formation, which is called positive pressure perforation.
B negative pressure perforation: when perforating, the pressure of liquid column in casing is less than formation pressure. After perforation, the oil and gas in the formation will flow to the wellbore, so that the cuttings produced by perforation can be washed away and the well fluid will not enter the formation. This is called negative pressure perforation. Negative pressure perforation can produce backflow to clean the borehole and eliminate secondary pollution, thus greatly improving the productivity of oil and gas wells. Negative pressure perforation is the best perforation method, but it is not feasible to realize negative pressure perforation by cable transportation. Through-tubing perforation can only form negative pressure in the first shot, and the second shot and later are equal pressure perforation. However, due to the limitation of the length of wellhead BOP, the length of gun perforating through tubing is limited, and only a few wells only shoot one gun, so perforating through tubing can not meet the requirements of negative pressure perforation. Only TCP can meet the requirements of negative pressure perforation.
(2) Offshore tubing delivery perforator
Tubing transport perforation (TCP) is to transport perforating equipment underground with tubing or drill pipe for perforation. The same as cable conveying perforation, it uses four kinds of initiating explosive devices: detonator, detonating cord, booster tube and perforating bullet, and is also suitable for perforating guns with various casings.
1. Perforation characteristics of tubing transportation
Different from cable conveying perforation, the only difference is the way of conveying and initiating, which is characterized by:
Strong transportation capacity, can shoot hundreds of meters of oil and gas layers at a time, and the operation efficiency is high;
The use of large caliber, high hole density perforating gun and high explosive charge can meet the perforation requirements of high penetration depth and large aperture;
According to the design requirements, a large negative pressure difference is formed, which can fully clean the perforation and eliminate the secondary pollution;
Achieve high production ratio and improve single well production;
Put into production immediately after perforation, with quick effect;
Install control facilities such as wellhead and underground safety joint before initiation to ensure safety;
Determine the productivity of formation together with DST test;
Wide application range: it is suitable for highly deviated wells, horizontal wells, high-pressure oil and gas wells, corroded wells, gravel packing wells, double-tube oil production wells, pumping wells and so on.
2. Tubing conveying perforation string structure
Figure 7-73 Structure of Tubing Conveying Perforation String
Tubing perforation string (Figure 7-73) includes perforating guns, detonating devices and downhole tools. They are connected together by tubing or variable joint, which is called TCP perforation string. Its function is to facilitate the detonation of the perforating gun to open the oil and gas reservoir, so that oil and gas can smoothly flow into the production string and generate negative pressure between the production string and the formation, and it can be used to disarm the perforating gun and salvage the ignition matches. As shown in Figure 7-73, the common pipe string structure of TCP consists of guide shoe, perforating gun, safety nipple (empty grab), detonating device, production valve (anti-pollution circulating joint or negative pressure valve, perforating pipe), releasing device, packer, radioactive positioning joint, etc. From bottom to top, it can be increased or decreased according to the situation of oil and gas wells and the purpose of construction, such as adding shock absorbers for formation testing.
A. Perforating gun: it is the carrier for sending initiating explosive devices underground. Perforator is the general name of perforating gun assembled by perforating charge, detonating cord, booster tube, detonator, gun head, gun tail and intermediate joint.
B. Perforating charge: the core component that penetrates casing, cement sheath and formation in perforating operation. The charge type of perforating charge is selected according to the penetration depth of perforating charge, downhole temperature and firing time required by users.
C. Ignition head: The ignition head is also called the initiating device. Generally speaking, the whole process of shaped charge perforation is that the impact detonator is detonated, and after detonation transmission and detonation initiation, the perforating bullet finally releases all energy to form a high-pressure and high-speed jet to penetrate the target. It is a key component of TCP. There are many kinds of ignition heads. At present, the safety mechanical ignition head is widely used in TCP operation at sea, which is divided into low pressure and high pressure. When the ignition match hits the release rod, the shear pin is sheared, and the downward movement of the release rod makes the steel ball move to the left, thus releasing the piston striker, which moves downward to ignite the detonator and detonate it under the pressure of the liquid cushion in the pipe string.
Second, the drilling test technology
Testing technology in the middle of drilling, that is, wireline formation testing technology, is an important means to evaluate oil and gas reservoirs. Before the 1990s, the oil and gas reservoir test in the middle of drilling was mainly completed by the drill string test, which usually took several days. In recent years, a new testing technology has appeared abroad, that is, using wireline formation tester to measure formation pressure, obtaining original formation fluid by pumping technology, and calculating formation productivity by using other logging data, achieving the same effect as drill pipe testing. Generally, this operation can be completed in dozens of hours, saving time and effort, with high efficiency and low cost. It has increasingly replaced drill pipe testing and become a very promising exploration technology.
At present, Schlumberger's Repetitive Formation Tester (RFT) or Atlas's Formation Tester (FMT) are widely used in China, but their design, function and measurement results are not ideal, so it is difficult to calculate the permeability of the test layer and accurately judge the fluid properties. The most important thing is that the original fluid of the reservoir can't be obtained, especially in the deeply invaded strata, and the fluid samples obtained are basically mud-polluted fluids, so it is difficult to accurately predict the productivity.
In order to break the monopoly of foreign technology, fill the gap, replace the import, reduce the well occupation time, reduce the cost, meet the needs of offshore exploration and development, and make a detailed evaluation of the reservoir in time, the head office applied for the topic of "wireline drilling oil and gas reservoir testing technology" in the national "863" plan. This shows that with the support of the state, the research on wireline formation testing technology with independent intellectual property rights aims at developing formation parameter logging instruments that can directly provide authoritative, accurate, comprehensive and rapid completion of open hole formation testing for offshore oil and gas reservoir evaluation. The instrument adopts advanced modular design, while maintaining the original state of the reservoir, it ensures that most of the data needed for reservoir engineering can be obtained completely and accurately during the sampling process, so as to predict the reservoir productivity, maximize the oil and gas recovery, and reduce the testing cost and expense. Specific applications include: ① measuring formation pressure, and confirming the results through repeated measurements; ② Collecting formation fluid samples under real formation conditions; ③ Calculation of formation permeability; (4) identifying low pressure or overpressure areas; ⑤ Determine the gravity and related depth of reservoir fluid; ⑥ Calculate the fluidity and compressibility of formation fluid; ⑦ Vertical distribution of reservoir pollution coefficient.
Brief introduction of (1) cable formation tester
1. structure
The instrument adopts modular design, and each module realizes certain functions. Modules can be arbitrarily combined as required. The instrument is designed into five modules, namely the electronic circuit module; Hydraulic source module; Packer module; Fluid identification module; High pressure fluid pump module; PVT sampling module; Joint sample control module, etc. (Figure 7-74).
The functions of each module are as follows.
(1) hydraulic source module
For the hydraulic power system of the instrument, the pressure of 4500psi is provided by the hydraulic pump, and the pressure is transmitted through the hydraulic pipeline to drive the expansion and contraction of the packer and the mechanical action of each module.
(2) Packer module
Mud is sealed with the formation, and the formation fluid enters the instrument body through the probe of the sealer for testing and sampling.
Figure 7-74 Cable Formation Tester Structure
(3) Electronic circuit
Complete the electronic control of downhole mechanical actions, such as packer expansion and contraction, fluid extraction, fluid pumping, fluid sampling and sensor signal acquisition.
(4) fluid identification module
In order to obtain a real formation fluid sample, it is necessary to discharge the contaminated fluid from the borehole wall into the wellbore, and judge whether the fluid is a real formation fluid by resistivity, density or frequency spectrum.
(5) High pressure fluid pump
A high-pressure fluid pump discharges fluid from the formation into the wellbore.
(6) Movable sampling cylinder
The obtained formation fluid samples are loaded into the sampling barrel for transportation to the laboratory for composition analysis.
2. Working principle
The instrument can measure formation pressure and extract formation fluid samples.
(1) pressure measurement
Figure 7-74 Schematic Diagram of Fluid Pressure Measurement
The instrument is sent to the target layer by cable, and the packer is opened under the control of the ground, as shown in Figure 7-75. The packer seals the formation near the borehole wall, the fluid prediction chamber is opened, and the formation fluid is sucked into the prediction chamber. At this point, the sensor in the prediction room measures the formation pressure, and the pressure curve is shown in Figure 7-76.
(2) sampling
After the formation pressure test is completed, samples should be taken. In order to obtain real samples of formation fluids and remove contaminated fluids such as mud, these contaminated fluids must be discharged first. At this point, the hydraulic motor begins to discharge formation fluid into the wellbore. The resistivity of the fluid is always monitored during the discharge process. When the resistivity of the discharged fluid tends to be stable, the fluid is the real fluid in the formation at this time, and sampling action is carried out. As shown in figures 7-77 and 7-78.
Figure 7-76 Relationship between Formation Pressure Recovery and Test Time
A-b- hydrostatic pressure; B-CB-C —— The packer pushes against the borehole wall and the fluid is compressed; C-d-fluid enters the instrument and is decompressed; D-e- mud cake falls off and the pressure rises; E-F —— Assuming that the pressure in the invasion zone is higher than the formation pressure, the mud filtrate flows and the pressure drops; F-c- the suction pressure is lower than the formation pressure; Pressure recovery
Figure 7-77 Discharge of formation pollution fluid
Figure 7-78 Open the sampling cylinder
(2) Research on formation tester.
In this paper, a set of downhole pumping fluid sampling tester and its interpretation system are studied. Through its pumping system, the real samples of formation fluid can be obtained, and the parameters such as permeability, pressure distribution and productivity of oil and gas reservoirs can be calculated through pressure test curves, which partially replaces the midway oil testing technology. The main research contents include the following five aspects.
1. Simulation experimental model and numerical simulation
The simulation model adopts three-dimensional cylinder or sphere structure to simulate complex borehole and formation conditions. The response characteristics of the instrument under different formation pressure, different fluid saturation, different permeability, different mud cake thickness and different drainage speed are studied by simulation experiments, and the relationship between formation characteristics and numerical response of the instrument is established. According to different reservoir conditions in Bohai Oilfield, models of different formation pressures and fluids are established, and a series of experimental data are obtained. The key considerations are as follows: ① the special requirements of shallow weakly cemented loose sandstone for instruments and interpretation models; (2) Skin effect and storage effect under the condition of heavy oil exploitation; ③ Influence of sand production on the model.
Considering the reservoir characteristics of onshore oil and gas fields, the simulation is carried out in a targeted manner. The anisotropic unsteady seepage model with pipeline storage and skin effect is studied. The analytical solution of double probe anisotropy is studied. The phase delay seepage model of harmonic pressure pulse is studied. The double-probe finite element simulation method is studied.
2. Structural design and manufacture of hydraulic power system
The downhole instruments of oil and gas reservoir testing while drilling technology include electronic circuit, hydraulic power system, packer system, pumping system, real-time identification system of fluid characteristics, reverse injection module, PVT (pressure, volume and temperature) sampling cylinder and large sampling control module. The design of these modules should not only meet the engineering requirements, but also consider the requirements of harsh well conditions such as high temperature and high pressure caused by specific working environment. Because these systems are very precise mechanical devices, it is quite difficult to design and manufacture such instruments. Specifically, the design of the volume, power and temperature of the hydraulic source; Design of hydraulic circuit and hydraulic valve system; Distance design under the influence of two detectors in three-dimensional dynamic fluid model: the design and manufacture of high-pressure drainage pump under complex formation conditions are studied; Reverse fluid injection technology under different fluids and different formation pressures; Automatic fluid identification technology; Research on sampling control and sample preservation technology.
3. Design and manufacture of electronic control and data transmission module.
The underground electronic circuit has two main functions: one is to receive and decode the instructions from the ground, control various mechanical actions of underground instruments, and monitor various states of instruments; The second is to collect converted data and transmit the data to the ground for processing. In particular to an MPU microprocessor control circuit. Relay control circuit; Various sensor signal processing circuits; Data acquisition, processing and transmission.
4. Ground support system
Including the ground panel and system software, all downhole functions of the oil and gas reservoir characteristic logging tool are controlled by the ground system. Including the recording of test data, the ground adjustment of different test parameters (such as the determination of pressure measuring sampling points, the selection of predicted volume, the selection of pump displacement and pressure drop, etc.). ), the judgment of downhole working conditions and the nature of sampling fluid. Its pumping system can synchronously monitor the liquid flowing through the instrument or pumped into the sampling cylinder, and calculate its characteristic parameters. The realization of these functions needs the support of ground software.
5. Test system design, data interpretation model research and interpretation software development.
A. Design methods of testing working systems for different oil and gas reservoirs. In view of the complex conditions of heavy oil, low permeability, oil, gas and water multiphase, the reasonable test working system with short test time, small flow rate and small displacement, the time control of pump displacement and the design of multi-probe vertical interference test are studied.
B. Quantitative interpretation of low-speed short-time pressure data and development of a new model for interpretation. Superposition analysis of spherical and cylindrical pressure drop and pressure recovery, typical curve analysis considering the storage and skin effect of pipeline wells, flow period identification and flow model, multi-layer model, composite model, multiphase flow model, vertical interference model, reverse injection model and reservoir boundary analysis model.
C. Comprehensive evaluation and research methods of oil and gas reservoirs by using 3D seismic, drilling, logging and reservoir engineering. Determine the appropriate drilling fluid, completion design and reservoir development suggestions, and study the short-term test productivity prediction technology that partially replaces DST.
D. data interpretation software system.
The key technologies of the above research include three-dimensional simulation model research and numerical simulation calculation; High temperature and high pressure micro-hydraulic power system: double packer system; Spectral fluid identification technology; Fluid sampling and sample preservation technology; Underground real-time automatic control system; Ground measurement and control system; Data interpretation method of complex reservoir; Reverse fluid injection technology.
The successful development of formation testing technology will solve the major geological problems in oil and gas exploration: repeated sampling and repeated testing will make pressure measurement more accurate; Mud filtrate is discharged by pumping technology to obtain undisturbed formation fluid samples; Double packer technology ensures that formation fluid samples can be obtained in any rock formation, and solves the problem of sampling blockage in heavy oil siltstone with single packer; It will gradually replace oil testing technology, become an important tool for formation evaluation, and provide a favorable tool for reducing costs. In addition, in view of the fact that there is no good open hole layered testing technology for oil and gas in China at present, it can be used as layered dynamic testing and sampling testing for offshore or onshore oil exploration wells and development wells, and it is an excellent layered dynamic direct measurement technology. This dynamic sampling test is needed for every oil and gas well in the ocean and on land. With the unprecedented and complete dynamic data of reservoir stratification, we can accurately and perfectly understand the oil layer and each stratification, and apply the test results to all links of oil and gas exploration, oil field development and oil production engineering, which is conducive to oil and gas exploration and oil and gas field development with high quality, high speed and high efficiency. Furthermore, logging instruments aiming at reservoir characteristics will have independent intellectual property rights, have the legal status of domestic and international market competition, and can break through various restrictions and provide such logging technical services to foreign countries, thus obtaining better economic benefits.