Sustained casing pressure （SCP） in gas wells brings a serious threat to worker safety and environmental protection. According to geological conditions, wellbore structure and cement data of gas wells in the Sichuan-...Sustained casing pressure （SCP） in gas wells brings a serious threat to worker safety and environmental protection. According to geological conditions, wellbore structure and cement data of gas wells in the Sichuan-Chongqing region, China, the position, time, environmental condition and the value of SCP have been analyzed. On this basis, the shape of the pressure bleed-down plot and pressure buildup plot were diagnosed and the mechanism of SCP has been clarified. Based on generalized annular Darcy percolation theory and gas-liquid two-phase fluid dynamics theory, a coupled mathematical model of gas migration in a cemented annulus with a mud column above the cement has been developed. The volume of gas migrated in the annulus and the value of SCP changing with time in a gas well in Sichuan have been calculated by this model. Calculation results coincided well with the actual field data, which provide some reference for the following security evaluation and solution measures of SCP.展开更多
Sustained casing pressure(SCP)is a crucial issue in the oil and gas production lifecycle.Epoxy resins,exhibiting exceptional compressive strength,ductility,and shear bonding strength,have the potential to form reliabl...Sustained casing pressure(SCP)is a crucial issue in the oil and gas production lifecycle.Epoxy resins,exhibiting exceptional compressive strength,ductility,and shear bonding strength,have the potential to form reliable barriers.The injectivity and sealing capacity of the epoxy resin is crucial parameters for the success of shallow remediation operations.This study aimed to develop and assess a novel solid-free resin sealant as an alternative to Portland cement for mitigating fluid leakage.The investigation evaluated the viscosity,compressive strength,and brittleness index of the epoxy resin sealant,as well as its tangential and normal shear strengths in conjunction with casing steel.The flow characteristics and sealing abilities of conventional cement and epoxy resin were comparatively analyzed in cracks.The results showed that the application of a viscosity reducer facilitated control over the curing time of the epoxy resin,ranging from 1.5 to 6 h,and reduced the initial viscosity from 865.53 to 118.71 m Pa,s.The mechanical properties of the epoxy resin initially increased with a rise in curing agent content before experiencing a minor decrease.The epoxy resin containing 30%curing agent exhibited optimal mechanical properties.After a 14-day curing period,the epoxy resin's compressive strength reached81.37 MPa,2.12 times higher than that of cement,whereas the elastic modulus of cement was 2.99 times greater than that of the epoxy resin.The brittleness index of epoxy resin is only 3.42,demonstrating high flexibility and toughness.The tangential and normal shear strengths of the epoxy resin exceeded those of cement by 3.17 and 2.82 times,respectively.In a 0.5 mm-wide crack,the injection pressure of the epoxy resin remained below 0.075 MPa,indicating superior injection and flow capabilities.Conversely,the injection pressure of cement surged dramatically to 2.61 MPa within 5 min.The breakthrough pressure of0.5 PV epoxy resin reached 7.53 MPa,decreasing the crack's permeability to 0.02 D,a mere 9.49%of the permeability observed following cement plugging.Upon sealing a 2 mm-wide crack using epoxy resin,the maximum breakthrough pressure attained 5.47 MPa,3.48 times of cement.These results suggest that epoxy resin sealant can be employed safely and effectively to seal cracks in the cement.展开更多
The author have in recent years treated 42 cases of intractable insomnia (with a history of over 2 years) by point pressure, yielding quite satisfactory results when compared with those treated with clonazepam. Th... The author have in recent years treated 42 cases of intractable insomnia (with a history of over 2 years) by point pressure, yielding quite satisfactory results when compared with those treated with clonazepam. This is reported as follows.……展开更多
With the development of cementing slurry technology,cementing self-healing has become one of the most effective technologies to prevent and treat oil and gas channeling and improve long-term sealing capacity of cement...With the development of cementing slurry technology,cementing self-healing has become one of the most effective technologies to prevent and treat oil and gas channeling and improve long-term sealing capacity of cement sheath.To solve the technical problem of annulus oil and gas channeling caused by the long-term sealing failure of cement sheath,this paper researches and develops a kind of viscosity-soluble type biomimetic self-healing cement slurry system from the perspective of chemical biomimetics,based on the technical idea of“prevention before blocking”.Then,the engineering performance of this biomimetic self-healing cement slurry system and the mechanical property of self-healing set cement are evaluated respectively.In addition,the mechanical recovery capacity and permeability reducing rate of the self-healing set cement conserved with methane are evaluated by creating fractures through splitting.Finally,the healing mechanisms of the self-healing cement are analyzed by means of SEM microscopic test and infrared spectrography.And the following research results are obtained.First,the set cement has excellent mechanical property.When the compressive strength decreases by 15%,the elastic modulus of set cement decreases by 41%,showing good toughness to play the role of“first prevention”.Second,when meeting hydrocarbon,the damaged set cement is excited to generate a kind of viscosity-soluble type gelatinous ester substance,which re-bonds the skeleton of the set cement.When the self-healing set cement is conserved with methane,its compressive strength recovery rate is up to 94.5%,bending strength recovery rate is 58.6%,gas log permeability drops by 99%,and liquid log permeability drops by 100%,so as to realize“blocking later”.In conclusion,the viscosity-soluble type biomimetic self-healing cement slurry system can effectively achieve cementing integrity and long-term sealing integrity through self-healing after the damage of cement sheath,which provides a strong technical support for preventing the production safety hazard of sustained casing pressure in oil and gas wells and is beneficial to solve the technical problem of annulus oil and gas channeling caused by long-term sealing failure of cement sheath.展开更多
Kick tolerance is a key parameter to indicate whether shut-in operation can be carried out safely and a proper well killing method should be chosen in well drilling.At present,however,the calculation of kick tolerance...Kick tolerance is a key parameter to indicate whether shut-in operation can be carried out safely and a proper well killing method should be chosen in well drilling.At present,however,the calculation of kick tolerance in deepwater drilling is not efficient enough.In this paper,a calculation method for volume kick tolerance of deepwater drilling was developed by means of theoretical derivation and example verification.Based on deepwater borehole temperature profile,choke manifold and annulus circulating pressure loss,the calculation model of volume kick tolerance was established under the constraint of the pressure-bearing capacity of the formation at the casing shoe,resistance to internal pressure of casing,blowout preventer(BOP)and choke control.Then,its reliability was verified by using the calculation results of a deepwater well in the South China Sea.It is indicated that the well can be shut in safely and the well killing will be safer if the Engineer's Method is used.The result is in agreement with the measures that were adopted on site.Finally,the newly developed calculation model was compared with those which don't take temperature and pressure loss into account,and the effect of choke manifold,annulus pressure loss and temperature inside wellbore on kick tolerance was analyzed.It is shown that the volume kick tolerance will get smaller if the effect of pressure loss and temperature is not taken into account,and the well killing conditions will be more rigorous.In addition,the technical measures to increase kick tolerance were proposed after the influential laws of pit gain and overflow depth on kick tolerance were analyzed.展开更多
基金co-financed by the China National Natural Science Foundation and Shanghai Baosteel Group Corporation (No. 51074135)Program for New Century Excellent Talents in University (No. NCET-08-0907)Jilin Oilfield Company Project (No. JS10-W-14-JZ-32-51)
文摘Sustained casing pressure （SCP） in gas wells brings a serious threat to worker safety and environmental protection. According to geological conditions, wellbore structure and cement data of gas wells in the Sichuan-Chongqing region, China, the position, time, environmental condition and the value of SCP have been analyzed. On this basis, the shape of the pressure bleed-down plot and pressure buildup plot were diagnosed and the mechanism of SCP has been clarified. Based on generalized annular Darcy percolation theory and gas-liquid two-phase fluid dynamics theory, a coupled mathematical model of gas migration in a cemented annulus with a mud column above the cement has been developed. The volume of gas migrated in the annulus and the value of SCP changing with time in a gas well in Sichuan have been calculated by this model. Calculation results coincided well with the actual field data, which provide some reference for the following security evaluation and solution measures of SCP.
基金funded by the National Natural Science(Grant No.52274015)。
文摘Sustained casing pressure(SCP)is a crucial issue in the oil and gas production lifecycle.Epoxy resins,exhibiting exceptional compressive strength,ductility,and shear bonding strength,have the potential to form reliable barriers.The injectivity and sealing capacity of the epoxy resin is crucial parameters for the success of shallow remediation operations.This study aimed to develop and assess a novel solid-free resin sealant as an alternative to Portland cement for mitigating fluid leakage.The investigation evaluated the viscosity,compressive strength,and brittleness index of the epoxy resin sealant,as well as its tangential and normal shear strengths in conjunction with casing steel.The flow characteristics and sealing abilities of conventional cement and epoxy resin were comparatively analyzed in cracks.The results showed that the application of a viscosity reducer facilitated control over the curing time of the epoxy resin,ranging from 1.5 to 6 h,and reduced the initial viscosity from 865.53 to 118.71 m Pa,s.The mechanical properties of the epoxy resin initially increased with a rise in curing agent content before experiencing a minor decrease.The epoxy resin containing 30%curing agent exhibited optimal mechanical properties.After a 14-day curing period,the epoxy resin's compressive strength reached81.37 MPa,2.12 times higher than that of cement,whereas the elastic modulus of cement was 2.99 times greater than that of the epoxy resin.The brittleness index of epoxy resin is only 3.42,demonstrating high flexibility and toughness.The tangential and normal shear strengths of the epoxy resin exceeded those of cement by 3.17 and 2.82 times,respectively.In a 0.5 mm-wide crack,the injection pressure of the epoxy resin remained below 0.075 MPa,indicating superior injection and flow capabilities.Conversely,the injection pressure of cement surged dramatically to 2.61 MPa within 5 min.The breakthrough pressure of0.5 PV epoxy resin reached 7.53 MPa,decreasing the crack's permeability to 0.02 D,a mere 9.49%of the permeability observed following cement plugging.Upon sealing a 2 mm-wide crack using epoxy resin,the maximum breakthrough pressure attained 5.47 MPa,3.48 times of cement.These results suggest that epoxy resin sealant can be employed safely and effectively to seal cracks in the cement.
文摘 The author have in recent years treated 42 cases of intractable insomnia (with a history of over 2 years) by point pressure, yielding quite satisfactory results when compared with those treated with clonazepam. This is reported as follows.……
基金supported by Scientific Research and Technology Development Project of PetroChina Southwest Oil&Gasfield Company“Evaluation method of self-healing slurry”(No.20220302-02).
文摘With the development of cementing slurry technology,cementing self-healing has become one of the most effective technologies to prevent and treat oil and gas channeling and improve long-term sealing capacity of cement sheath.To solve the technical problem of annulus oil and gas channeling caused by the long-term sealing failure of cement sheath,this paper researches and develops a kind of viscosity-soluble type biomimetic self-healing cement slurry system from the perspective of chemical biomimetics,based on the technical idea of“prevention before blocking”.Then,the engineering performance of this biomimetic self-healing cement slurry system and the mechanical property of self-healing set cement are evaluated respectively.In addition,the mechanical recovery capacity and permeability reducing rate of the self-healing set cement conserved with methane are evaluated by creating fractures through splitting.Finally,the healing mechanisms of the self-healing cement are analyzed by means of SEM microscopic test and infrared spectrography.And the following research results are obtained.First,the set cement has excellent mechanical property.When the compressive strength decreases by 15%,the elastic modulus of set cement decreases by 41%,showing good toughness to play the role of“first prevention”.Second,when meeting hydrocarbon,the damaged set cement is excited to generate a kind of viscosity-soluble type gelatinous ester substance,which re-bonds the skeleton of the set cement.When the self-healing set cement is conserved with methane,its compressive strength recovery rate is up to 94.5%,bending strength recovery rate is 58.6%,gas log permeability drops by 99%,and liquid log permeability drops by 100%,so as to realize“blocking later”.In conclusion,the viscosity-soluble type biomimetic self-healing cement slurry system can effectively achieve cementing integrity and long-term sealing integrity through self-healing after the damage of cement sheath,which provides a strong technical support for preventing the production safety hazard of sustained casing pressure in oil and gas wells and is beneficial to solve the technical problem of annulus oil and gas channeling caused by long-term sealing failure of cement sheath.
文摘Kick tolerance is a key parameter to indicate whether shut-in operation can be carried out safely and a proper well killing method should be chosen in well drilling.At present,however,the calculation of kick tolerance in deepwater drilling is not efficient enough.In this paper,a calculation method for volume kick tolerance of deepwater drilling was developed by means of theoretical derivation and example verification.Based on deepwater borehole temperature profile,choke manifold and annulus circulating pressure loss,the calculation model of volume kick tolerance was established under the constraint of the pressure-bearing capacity of the formation at the casing shoe,resistance to internal pressure of casing,blowout preventer(BOP)and choke control.Then,its reliability was verified by using the calculation results of a deepwater well in the South China Sea.It is indicated that the well can be shut in safely and the well killing will be safer if the Engineer's Method is used.The result is in agreement with the measures that were adopted on site.Finally,the newly developed calculation model was compared with those which don't take temperature and pressure loss into account,and the effect of choke manifold,annulus pressure loss and temperature inside wellbore on kick tolerance was analyzed.It is shown that the volume kick tolerance will get smaller if the effect of pressure loss and temperature is not taken into account,and the well killing conditions will be more rigorous.In addition,the technical measures to increase kick tolerance were proposed after the influential laws of pit gain and overflow depth on kick tolerance were analyzed.
