Most fault-block reservoirs in Xinmu oilfield belong to heterogeneous sandstone in characters which has low permeability, and reservoir pollution is a common phenomenon in this area. Acidizing deplugging in oil wells ...Most fault-block reservoirs in Xinmu oilfield belong to heterogeneous sandstone in characters which has low permeability, and reservoir pollution is a common phenomenon in this area. Acidizing deplugging in oil wells has become one of the major measures to improve production efficiency in the field. A compound deplug- ging technology in high efficiency low corrosion is developed for this kind of low permeability sandstone reser- voir. On the basis of profoundly understanding of the reservoir＇s physical properties and sensitivity, along with comprehensive analysis of the cause for jams in oil wells, a series of experiments are carried out in order to in- vestigate the dissolution reaction among samples and deplugging inhibitor, sample dissolving speed, formation fluid compatibility, reduction of secondary pollution, etc. Considered reservoir condition in nearby wells the op- timized compositional deplugging liquid formula is selected for this reservoir. It is featured by reducing the de- plugging reaction speed, extending solution for processing radius, preventing secondary damage in dissolution processing, and removing plug pollution effectively. To implement this high efficiency low corrosion deplugging measure based on reservoir condition in the borehole and nearby wells, a relatively better result of deplugging and production increasing is achieved, which enriches the measures to increase production in Xinmu oilfield, and this method can be applied to other similar oiffields for the purpose of maintaining the crude oil production and providing assistant for increasing the production significantly.展开更多
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 f...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.展开更多
In order to obtain the perforation depth, the three zones with different permeability because of plastic deformation and fluid invasion were studied based on related theories. The study shows that the calculation of p...In order to obtain the perforation depth, the three zones with different permeability because of plastic deformation and fluid invasion were studied based on related theories. The study shows that the calculation of perforation depth should take account of not only damaged zone, but also plastic zone, because the plastic zone has much lower permeability. The required minimum perforation depth was obtained by making the solution of elastic/plastic equations, and the factors affecting perforation depth were analyzed accordingly.展开更多
With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale ...With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale gas.In order to explore casing deformation prediction,prevention and treatment methods,this paper analyzes the geological and engineering causes of casing deformation in shale-gas horizontal wells through laboratory work,such as the casing resistance to internal pressure alternating test,the ground simulation test and systematical casing deformation characteristic analysis of MIT24 caliper logging,and the large-scale physical simulation test and numerical simulation of casing deformation.Then,combined with the generalized shear activity criterion,a new method for evaluating casing deformation risk points and some technical measures for preventing casing deformation were formulated.And the following research results were obtained.First,the deformation characteristics of 119 casing deformation points in 23 wells interpreted by MIT24 caliper logging are consistent with the mechanical behaviors of shear compression deformation test.Second,the large-scale physical simulation test shows that natural fault-fractures slip obviously under the state of strike-slip stress.Third,numerical simulation shows that the compression stress on casing increases with the increase of fault-fracture slip.When the fault-fracture slip is between 7.5 mm and 9.0 mm,the casing reaches the critical yield strength and begins to undergo plastic deformation.The“temporary fracture plugging+long segment and multi-cluster”and other technologies are field tested in 28 wells in Weiyuan area of southern Sichuan Basin.The casing deformation rate decreases from 54%(before this research)to 14.3%,and the segment loss rate decreases from 7.8%to 0,which reveals remarkable achievements in casing deformation treatment.In conclusion,the shear slip of fault and macro fractures(referred to as fault-fracture)is the main cause of casing deformation in shale gas horizontal wells,and some measures(e.g.“temporary fracture plugging+long segment and multi-cluster”,reducing fracturing scale and releasing wellbore pressure properly)shall be taken in advance to reduce the fault-fracture activity before the risk point of casing deformation is fractured,so as to reach the goal of casing deformation prevention.展开更多
文摘Most fault-block reservoirs in Xinmu oilfield belong to heterogeneous sandstone in characters which has low permeability, and reservoir pollution is a common phenomenon in this area. Acidizing deplugging in oil wells has become one of the major measures to improve production efficiency in the field. A compound deplug- ging technology in high efficiency low corrosion is developed for this kind of low permeability sandstone reser- voir. On the basis of profoundly understanding of the reservoir＇s physical properties and sensitivity, along with comprehensive analysis of the cause for jams in oil wells, a series of experiments are carried out in order to in- vestigate the dissolution reaction among samples and deplugging inhibitor, sample dissolving speed, formation fluid compatibility, reduction of secondary pollution, etc. Considered reservoir condition in nearby wells the op- timized compositional deplugging liquid formula is selected for this reservoir. It is featured by reducing the de- plugging reaction speed, extending solution for processing radius, preventing secondary damage in dissolution processing, and removing plug pollution effectively. To implement this high efficiency low corrosion deplugging measure based on reservoir condition in the borehole and nearby wells, a relatively better result of deplugging and production increasing is achieved, which enriches the measures to increase production in Xinmu oilfield, and this method can be applied to other similar oiffields for the purpose of maintaining the crude oil production and providing assistant for increasing the production significantly.
基金Supported by National Natural Science Foundation of China(51991361,52074327,U1762212)Major Engineering Technology Field Tes Project of CNPC(2020F-45)。
文摘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.
文摘In order to obtain the perforation depth, the three zones with different permeability because of plastic deformation and fluid invasion were studied based on related theories. The study shows that the calculation of perforation depth should take account of not only damaged zone, but also plastic zone, because the plastic zone has much lower permeability. The required minimum perforation depth was obtained by making the solution of elastic/plastic equations, and the factors affecting perforation depth were analyzed accordingly.
基金supported by the Scientific Research and Technology Development Project of CNPC“Research and field test of key technologies for effective exploitation of deep shale gas”(No.2019F-31JT).
文摘With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale gas.In order to explore casing deformation prediction,prevention and treatment methods,this paper analyzes the geological and engineering causes of casing deformation in shale-gas horizontal wells through laboratory work,such as the casing resistance to internal pressure alternating test,the ground simulation test and systematical casing deformation characteristic analysis of MIT24 caliper logging,and the large-scale physical simulation test and numerical simulation of casing deformation.Then,combined with the generalized shear activity criterion,a new method for evaluating casing deformation risk points and some technical measures for preventing casing deformation were formulated.And the following research results were obtained.First,the deformation characteristics of 119 casing deformation points in 23 wells interpreted by MIT24 caliper logging are consistent with the mechanical behaviors of shear compression deformation test.Second,the large-scale physical simulation test shows that natural fault-fractures slip obviously under the state of strike-slip stress.Third,numerical simulation shows that the compression stress on casing increases with the increase of fault-fracture slip.When the fault-fracture slip is between 7.5 mm and 9.0 mm,the casing reaches the critical yield strength and begins to undergo plastic deformation.The“temporary fracture plugging+long segment and multi-cluster”and other technologies are field tested in 28 wells in Weiyuan area of southern Sichuan Basin.The casing deformation rate decreases from 54%(before this research)to 14.3%,and the segment loss rate decreases from 7.8%to 0,which reveals remarkable achievements in casing deformation treatment.In conclusion,the shear slip of fault and macro fractures(referred to as fault-fracture)is the main cause of casing deformation in shale gas horizontal wells,and some measures(e.g.“temporary fracture plugging+long segment and multi-cluster”,reducing fracturing scale and releasing wellbore pressure properly)shall be taken in advance to reduce the fault-fracture activity before the risk point of casing deformation is fractured,so as to reach the goal of casing deformation prevention.
