Experimental study on the controlling factors of frictional coefficient for lost circulation control and formation damage prevention in deep fractured tight reservoir

Working fluids loss is a major contributor to low productivity during production process of fractured tight reservoirs.Lost circulation control effect directly related to the tribological behavior between fracture surface and lost circulation materials(LCMs).In this study,the friction coefficient(FC)was investigated using typical clastic rocks and LCMs by considering multiple effect factors divided into external condition and internal condition.The results show that normal load had a relatively high effect on sliding model.A positive correlation was observed between FC and asperities heights.FC decreased induced by particle size degradation of rigid LCMs.Elastic LCMs manifested higher FC compared with rigid LCMs.Under the lubrication condition by working fluid,FC of rigid LCMs was mainly controlled by their surface wettability.FC of organic LCMs is more sensitive to high temperature aging than inorganic LCMs.Fracture plugging experiments show that LCMs optimized based on the research results can effectively improve the efficiency and strength of fracture plugging.

Research progress and prospect of plugging technologies for fractured formation with severe lost circulation

By reviewing the mechanisms of drilling fluid lost circulation and its control in fractured formations, the applicability and working mechanisms of different kinds of lost circulation materials in plugging fractured formations have been summarized. Meanwhile, based on the types of lost circulation materials, the advantages, disadvantages, and application effects of corresponding plugging technologies have been analyzed to sort out the key problems existing in the current lost circulation control technologies. On this basis, the development direction of plugging technology for severe loss have been pointed out. It is suggested that that the lost circulation control technology should combine different disciplines such as geology, engineering and materials to realize integration, intelligence and systematization in the future. Five research aspects should be focused on:(1) the study on mechanisms of drilling fluid lost circulation and its control to provide basis for scientific selection of lost circulation material formulas, control methods and processes;(2) the research and development of self-adaptive lost circulation materials to improve the matching relationship between lost control materials and fracture scales;(3) the research and development of lost circulation materials with strong retention and strong filling in three-dimensional fracture space, to enhance the retention and filling capacities of materials in fractures and improve the lost circulation control effect;(4) the research and development of lost circulation materials with high temperature tolerance, to ensure the long-term plugging effect of deep high-temperature formations;(5) the study on digital and intelligent lost circulation control technology, to promote the development of lost circulation control technology to digital and intelligent direction.

Research progress and development of deep and ultra-deep drilling fluid technology

The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,high pressure and high stress,fracture development,wellbore instability,drilling fluid lost circulation and other problems faced in the process of deep and ultra-deep complex oil and gas drilling,scholars have developed deep and ultra-deep high-temperature and high-salt resistant water-based drilling fluid technology,high-temperature resistant oil-based/synthetic drilling fluid technology,drilling fluid technology for reservoir protection and drilling fluid lost circulation control technology.However,there are still some key problems such as insufficient resistance to high temperature,high pressure and high stress,wellbore instability and serious lost circulation.Therefore,the development direction of deep and ultra-deep drilling fluid technology in the future is proposed:(1)The technology of high-temperature and high-salt resistant water-based drilling fluid should focus on improving high temperature stability,improving rheological properties,strengthening filtration control and improving compatibility with formation.(2)The technology of oil-based/synthetic drilling fluid resistant to high temperature should further study in the aspects of easily degradable environmental protection additives with low toxicity such as high temperature stabilizer,rheological regulator and related supporting technologies.(3)The drilling fluid technology for reservoir protection should be devoted to the development of new high-performance additives and materials,and further improve the real-time monitoring technology by introducing advanced sensor networks and artificial intelligence algorithms.(4)The lost circulation control of drilling fluid should pay more attention to the integration and application of intelligent technology,the research and application of high-performance plugging materials,the exploration of diversified plugging techniques and methods,and the improvement of environmental protection and production safety awareness.

Research progress and application prospect of functional adhesive materials in the field of oil and gas drilling and production

By summarizing the composition,classification,and performance characterization of functional adhesive materials,the adhesion mechanisms of functional adhesive materials,such as adsorption/surface reaction,diffusion,mechanical interlocking,and electrostatic adsorption,are expounded.The research status of these materials in oil and gas drilling and production engineering field such as lost circulation prevention/control,wellbore stabilization,hydraulic fracturing,and profile control and water plugging,and their application challenges and prospects in oil and gas drilling and production are introduced comprehensively.According to the applications of functional adhesive materials in the field of oil and gas drilling and production at this stage,the key research directions of functional adhesive materials in the area of oil and gas drilling and production are proposed:(1)blending and modifying thermoplastic resins or designing curable thermoplastic resins to improve the bonding performance and pressure bearing capacity of adhesive lost circulation materials;(2)introducing low-cost adhesive groups and positive charge structures into polymers to reduce the cost of wellbore strengthening agents and improve their adhesion performance on the wellbore;(3)introducing thermally reversible covalent bond into thermosetting resin to prevent backflow of proppant and improve the compressive strength of adhesive proppant;(4)introducing thermally reversible covalent bonds into thermoplastic polymers to improve the temperature resistance,salt-resistance and water shutoff performance of adhesive water shutoff agents.

Development and Evaluation of a New Nanometer Based Spacer NMS-I

In view of the inadequate cementing quality in the cementation for long isolation intervals ofoil and gas wells, and considering the field practice in Tarim Oilfield, a nanometer material LC-212 was introduced as the base stock to experimentally develop a new spacer system NMS-I, in combination with other materials, including a chemical gel plugging agent, carboxymethyl cellulose and barite. Experimental results indicated that the system had a wide adjustable range of density, good rheological property, static stability and compatibility with cement slurry. It also showed no flocculating or thickening effect on the water-base drilling fluid and low-density cement system. Meanwhile, the capacity of lost circulation control and the influence of the spacer on the second interfacial cementing strength were evaluated by a self-made lost circulation simulator and shearing test facility. The results showed that the spacer had favorable plugging and flushing effect, and the second interfacial cementing strength can be greatly improved. Moreover, based on the experiments, the mechanisms of spacer function were analyzed. The results obtained from the investigation offer a novel approach to resolving some practical problems in cementing jobs.