2.3  Technical Benchmarking and Advantage Analysis

Compared with similar technologies in the world, the key technologies of intelligent oil and gas production independently developed by China are original and progressiveness, reaching the international advanced level on the whole. Some of them are at the international leading level, but some still have a big gap.

1) .There is a significant gap between underground monitoring and data transmission

Underground monitoring and data transmission are the key and difficult points to achieve layered development digitization, requiring more efficient, reliable, and economical underground monitoring transmission technology. Considering of the complexity of long-distance data transmission and line connections at the bottom of  the well, as well as the higher requirements for system reliability in harsh or extreme operating and production environments, obtaining real-time data from the wellbore and reservoir faces enormous challenges. There are still technical challenges in underground sensing, bidirectional communication, service cycle, and horizontal well adaptability. There is a significant gap between China and international advanced technologies, and China is currently in the stage of exploration and development.

2) .China has formed an intelligent technology system for the refined development of complex oil and gas reservoirs.

China has invented underground intelligent separate production and injection technology for the precise development of deep well and thin layer water injection reservoirs, and conducted intelligent technology experiments based on hydraulic control and electric control for separate injection and production; studied the adaptive flow regulation and water control completion technology and production control system to improve the balanced inflow profile of complex reservoirs, forming an intelligent production theory, method, and technical system for the effective development of inefficient wells. This technology has improved the level of intelligent development and innovative design of China's water drive old oilfields and low permeability and difficult to extract oil reservoirs. The level of this technical system is in line with international technology.

3) .China's onshore oil fields have implemented the "smart oil and gas production model" of new energy and intelligence.

China has built green oil production well pads, including new energy multi energy complementary microgrids; A series of "low-carbon and carbon reduction+" technologies such as intelligent injection and production, oil well interval pumping technology, hot washing and wax removal new processes, and new lifting technology, which will reduce energy consumption and carbon emissions from the source. The stable operation of multi energy complementary microgrid production collaborative control technology in dozens of well groups in Changqing Oilfield indicates that the combined innovative technology of "light wind power+DC bus+intelligent interval opening+motor flexible drive" has successfully entered the stage of large-scale application. Which have increased the energy efficiency and proportion of new energy in the production of oil well clusters, reduced CO2 emissions, and filled the gap in collaborative optimization technology for multi energy complementary microgrid pumping well clusters both domestically and internationally, meanwhile guaranteed the production capacity of the oil well.

3.Exploration of Intelligent Layered Injection and Production Technology for Onshore Oil and Gas Fields in China

With the development of onshore oil fields in China entering the mid to late stage, the interlayer contradictions in heterogeneous oil reservoir blocks are prominent. Layered exploitation and layered water injection are important means to resolve interlayer contradictions, fully utilize the production capacity of different permeability layers, maintain stable and high production of oil fields, improve the degree of oil reservoir utilization, and improve oil reservoir recovery rate. China has focused on the research and practice of intelligent technology for layered injection and production based on hydraulic control and electronic control; conducted research and on-site testing on the optimization of injection production wellbore and ground collaborative operation of the "multi energy complementary" microgrid; explored the optimization and control technology of injection and production unit production based on digital twins.

3.1 Intelligent Testing and Adjusting Technology for Production of Stratified Water Injection Wells

The domestic layered water injection process has gone through three development stages: fixed layered water injection, steel wire fishing layered water injection, and cable testing and adjustment layered water injection. China developed downhole storage sensor data communication technology for layered injection wells, cable direct reading communication and testing technology, preset cable real-time monitoring communication technology for downhole parameters, and downhole wireless communication technology. Emphasis has been placed on the development of cable permanent testing and injection technology, which can synchronously control multi-level underground testing devices for data monitoring and flow allocation. It can monitor injection pressure, flow rate, and temperature in real-time for each layer and control the opening of the plug, achieving fully automatic layered allocation and parameter monitoring.

The permanent cable testing and debugging system for injection wells consists of two parts: the wellhead and the underground. The wellhead is mainly composed of temperature, pressure and flow sensors, quantitative control valve, remote terminal unit (RTU) and edge computing integrated machine; The underground part mainly consists of electric water measuring and dispensing devices, cable positioning and sealing, cable insertion and sealing, steel pipe cables, temperature, pressure, flow sensors, etc. This system has the following functions:

•  Monitor the injection pressure, temperature, and flow rate at the wellhead;
•  Monitor the pressure, temperature, flow rate, etc. before/after the nozzle of each layer in the wellbore, and obtain real-time pressure values before and after the oil casing and water nozzle, instantaneous flow rate values of each injection layer, and water absorption index;
•  Monitor the working condition of the flow meter through pressure monitoring, and monitor the working condition of each sealing position through flow and pressure monitoring;
•  The underground electric water measuring and dispensing device adopts an electromechanical integrated design, integrating layered sealing inspection, layered water absorption testing, and layered water nozzle stepless control functions. According to the instructions of the ground measurement and tuning controller, the flow control mechanism of each layer regulates the movement status of the valve core, monitors the temperature, pressure, and injection amount of layered water injection in real-time, and quickly and automatically adjusts the opening of the water nozzle of the water dispenser.

This technology can operate at a depth of over 3800 meters, with a data transmission rate of 1 kb/s. It has good real-time data performance, large data volume, and integrated power supply and communication, effectively solving the problems of underground instrument power supply, underground monitoring, and data transmission. Currently, it has entered a demonstration application stage in layered water injection.

With the continuous deepening of oilfield development, the difficulty of its development is increasing, and the requirements for water injection technology are becoming higher and higher. It is still necessary to conduct in-depth research and strengthen research; We need to strengthen targeted research on layered water injection technology for high-temperature, high-pressure, low-permeability reservoirs, fractured karst cave type reservoirs, and buried hill fractured reservoirs; to conduct research on horizontal well layered water injection system and complex structure well layered water injection technology; to carry out research on intelligent testing and allocation integration technology, effectively improve the success rate of water well testing and adjustment construction, monitor the injection effect of injection wells, timely and effectively adjust the water injection volume, and ensure the qualified rate of water well layers.

3.2 Intelligent Testing and Adjusting Technology for Layered Oil Production Wells

The domestic layered oil production technology is mainly divided into two categories: water blocking layered oil production and layered production allocation. Specifically, there are underground intelligent layered oil production and measurement and control technology, vibration wave control layered oil production technology, bridge type separator layered oil production technology, and underground adjustable layered production allocation technology. Taking Daqing Oilfield as an example, with the continuous deepening of oilfield development process, the contradictions faced are constantly changing, and the functions and implementation methods of layered oil production technology are also evolving. From "self flowing layered production allocation" to "mechanical production well water blocking", and then to "hydraulic adjustable layer", it has developed to the current "intelligent layered oil production" with pre installed cable layered electric control. The supporting layered production tools, packer adjustment processes, etc. have also changed accordingly.

The pre installed cable layered electric control oil production control system is mainly composed of surface wellhead monitoring, underground data transmission, and underground dynamic monitoring and control systems. The underground dynamic monitoring and control system mainly consists of an underground parameter monitoring system with temperature, pressure, and flow sensors, and a flow regulator (i.e. intelligent production allocator). The cable is laid on the outer wall of the oil pipe and goes down from the wellhead to the bottom of the well, connecting the production allocator of each layer. The wellhead control command is transmitted to the production allocator of each layer underground through the cable, achieving layered production distribution. The cable supplies power to the production allocator at each layer of the well, and is also the carrier of two-way communication. The flow, pressure in front of the nozzle, pressure behind the nozzle, temperature and other parameters of each layer of the well can be transmitted to the ground in real time, and the downhole nozzle opening can be adjusted in real time according to the production dynamic changes through the surface edge computing integrated machine. This technology can achieve real-time monitoring of downhole state parameters and layered production allocation, and is a new generation of electrically controlled layered oil recovery technology.

The development of layered oil recovery technology has adapted to the production needs of various stages of oilfield development, and to a certain extent, solved the contradictions of phased production. In response to the low level of layered control in high water bearing oil fields, difficulties in finding and plugging water, high operating costs, and lack of effective long-term monitoring methods for downhole parameters, future layered oil recovery technology should focus on improving its technical level and adaptability, as well as the intelligent development of injection production integration and platformization.

3.3 Optimization and Control System for Injection Production Unit

Supported by the Internet of Things, cloud platform, edge computing and artificial intelligence, taking the reservoir injection and production process as the entity object, and taking mechanism simulation, indoor experiment, numerical simulation and digital twin as the means, the research on adaptive flow regulation and water control completion technology and production optimization control system of injection and production units was carried out, and new adaptive core controller and adaptive flow regulation and water control device were developed; We have formed an evaluation and testing system and optimized design methods, established a series of adaptive flow regulation and water control completion technologies and a composite technology system, expanded the window boundary of intelligent injection and production units, and improved the visualization level and scientific decision-making ability of the injection and production process.

3.3.1 Intelligent Control Technology for Production Parameters of Injection Production Wells from Injection End to Production End

A collaborative production control system for injection and production units based on real-time measurement and control technology for layered water injection and oil production, as well as dynamic optimization decision-making technology, can achieve dynamic real-time comprehensive perception of injection and production units, early warning of production abnormalities, online diagnosis of injection and production conditions, and intelligent regulation of wellbore parameters, reducing unplanned downtime and well repair operations, and saving oil production costs; Establishing an automatic matching and control mechanism between the injection end and the production end can improve the rate of oil and water well opening and operational efficiency, and reduce operational risks.

Real time collection of production parameters for injection and production wells, including single well (interval) flow and pressure, wellhead oil casing pressure, wellbore temperature and pressure distribution, and pipeline pressure, injection equipment pressurization and power, lifting equipment lift and power, etc, is achieved with the optimization objectives of recovery rate, production capacity, uniform injection/output profile, production rate, energy consumption, and injection and production equipment lifespan. The application mechanism and big data fusion method are used to create an intelligent optimization decision agent model for injection and production units based on real-time monitoring, which automatically matches and adjusts the operating parameters of injection and production equipment, such as the operating frequency of injection and production equipment and the opening of inflow control devices (ICDs), as shown in Figure 1.

Considering constraints such as layered injection volume, downhole injection valve nozzle loss-flow function, valve pressure, and valve opening, combined with the relationship equation between pressure difference and flow rate with different valve openings, real-time data is collected at the wellhead edge and a big data proxy model for water distributor opening adjustment is established through machine learning. Intelligent algorithms such as genetic algorithm, particle swarm optimization algorithm, and reinforcement learning are applied for automatic optimization, and by sending instructions to control the valve position through the wellhead testing controller, the flow area of the water nozzle can be adjusted, achieving fine regulation of each layer of the water injection well. Establishing a deep learning decision agent model method for layered oil recovery with the optimization goal of achieving balanced liquid supply in each section of the oil production well, and intelligently determining the number and spacing of ICDs in the horizontal wellbore; After determining the ICD distribution, real-time oil recovery parameters are collected at the edge of the wellhead, and an intelligent control model for ICD valve aperture based on deep reinforcement learning is proposed. The model tracks the dynamic environmental changes of the reservoir, automatically updates the reward/punishment mechanism, and optimizes the ICD valve opening with the well section pressure drop distribution as the optimization objective.