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Hole protection technology of complex stratum in core drilling
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Author:xingdacheng190221
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Published time: 2018-03-25
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Key words: complex stratum, hole protection technology
At first glance, the hole protection technology of drilling in complex strata seems to be large and empty, broad and abstract, as if it can be generalized and talked about.Not really. It's actually so small and specific that as soon as the drill starts, it's with you all the time, and there are endless "problems" around it.
An introduction to
The so-called complex strata, as we all know, are some strata due to the geological tectonic movement, the physical and chemical effects of the external environment and hydrogeological conditions, when drilling.Different degrees of hole collapse, leakage, water gushing and leakage, gushing, collapse occurred at the same time.People to produce these complex conditions of the strata, collectively referred to as complex strata.According to relevant statistics, only about 30% of engineering meters occur in the geological drilling of complex strata, while the engineering cost to complete these engineering quantities accounts for more than 60% of the total engineering cost, and more than 95% of engineering quantities discarded due to accidents occur in the drilling of these complex strata.Further analysis of the reasons, it is not difficult to see that these distressing scrap amount, and most of it is due to drilling in complex strata, the hole protection technology can not keep up.
The hole protection technology of complex stratum
1. In the process of drilling, unstable strata often encounter collapse and dropping of blocks inside the hole, as well as various degrees of encounter with resistance, stuck drilling, buried drilling accidents, borehole shrinkage and oversize, etc., which are collectively referred to as unstable strata.Unstable formation dynamic unstable formation and water sensitive unstable formation.
1.1 mechanical unstable stratum: refers to the multidirectional compression caused by geological origin or tectonic movement.The force inside the stratum is unbalanced, and once drilled through, the original equilibrium state is destroyed. In addition, unstable collapse and dropping of the hole wall are caused by gravity.For example, the 5 boreholes we drilled in no.56 mining area of jinchuan company belong to this geological feature, with 0 ~ 15m miscellaneous fill, 15 ~ 35m gravel layer, 35 ~ 55m gravel sand layer and 55 ~ 80m gneiss diorite. It is not difficult to see from the above that 55m is a mechanically unstable stratum before.To deal with this kind of stratum, we use the traditional mud as soon as we open the hole, adjust the consistency to make it reach the flow plastic state, and then use the screw pump which is good at transporting the mud to send the slurry to the drilling hole circulation, to ensure the drilling construction, this hole protection technology can basically complete the hole protection requirements of this stratum;In the gravel layer with strict requirements for core mining, we used SM vegetable gum drilling fluid with a concentration of 4% and a viscosity of more than 300 seconds. The hole protection effect was good during drilling, and the "core" cemented into a column could be taken out.For the fractured zone deep in the formation, the drilling fluid with excellent performance is used to pass through the zone quickly on the principle of "less vibration, faster passing".If PHP with high molecular weight is used, the concentration is adjusted to 500 ~ 1000ppm. Under the condition of not running the pump, hole drilling is carried out. This special well protection fluid is used in the 280-300m hole section of zk56-3.
1.2 water-sensitive strata: the simple definition is that the rock strata on the pore wall are loose, soft, expanded and spalling due to hydrolysis and hydration caused by the intrusion of washing fluid. The strata with such phenomenon are called water-sensitive strata.For example, in the 170m ~ 185m hole section of the zk56-3 well in the second mining area of jinchuan company, the formation is seriously petrified of green mud, and the broken diorite between layers is largely cemented with clay. When drilling in this section, the borehole is obviously manifested as shrinkage, collapse and drilling swaddling, and the washing fluid is seriously infected.The most prominent feature of such strata is water resistance. Therefore, in the drilling process, the first step is to prevent free water from contacting or infecting these strata, so as to avoid hydration of the rock-soil surface of these strata.In addition, it is necessary to supplement and increase the ion concentration in the medium of the flushing solution, such as K+, Na+, Ca2+, etc., so as to make it balance with the ion concentration of water in the rock formation, prevent the infiltration and hydration of the rock formation, so as to facilitate the stability of the pore wall.Integrated the hydration mechanism of the water sensitivity formation, should let the drilling rinses have such two characteristics: one is water loss is small, the second is considerable ion concentration, we the special hole section of drilling and to formulate the corresponding countermeasures, will rinses and related treatment parameters have been adjusted: (1) choose efficient water loss, like potassium humate and modified starch PGS double agent;(2) choose quality flocculant, such as molecular weight in more than 3 million, 30% of the degree of hydrolysis of polyacrylamide PAM;(3) add the optimal inorganic salt, such as KCL anti-collapse.The specific parameters we selected were 1000ppmmPHP, 5% PGS and 5% potassium humate, supplemented with 2-5% KCL.In this section, basically played a "waterproof, hole protection" purpose.
2 gushing and leaking formation
For general lost formation, relatively easy to deal with, as long as in drilling, control the specific gravity of the flushing fluid and supplemented by inert materials or plugging slurry, can basically block the leakage channel.The zk56-3 hole in the second mining area of jinchuan company can be said to be full hole leakage. For the general leakage layer, we mainly use 801 plugging agent and high concentration PAM, supplemented by inert materials such as sawdust and sheep manure.To deal with the larger leakage hole section, the general use of grouting to plug, can be used to try a strong water resistance, quick setting performance of viscoelastic grouting mixture, in fact, the formula is: water cement ratio of 0.5 ordinary Portland cement, 3% calcium chloride, 1% concentration of the molecular weight of the unhydrolyzed in 300 ~ 600 104 PAM aqueous solution.For the stratum with both leakage and surge, it costs money and time to treat with chemical well cleaning fluid, and the effect is not very ideal, so in the construction of zk56-3 hole, we used the traditional mud hole protection technology to quickly pass through the gushing and leaking layer, and then run the casing to isolate, the effect is good.
Three conclusions
When core drilling is carried out in complex strata, it is necessary to give priority to technological design and scientific construction.For unstable strata, the combination of traditional mud and chemical flushing liquid with scientific formula is used for hole protection.The traditional hole protection technology of mud and casing isolation should be emphasized in the formation with gushing and leaking.
At first glance, the hole protection technology of drilling in complex strata seems to be large and empty, broad and abstract, as if it can be generalized and talked about.Not really. It's actually so small and specific that as soon as the drill starts, it's with you all the time, and there are endless "problems" around it.
An introduction to
The so-called complex strata, as we all know, are some strata due to the geological tectonic movement, the physical and chemical effects of the external environment and hydrogeological conditions, when drilling.Different degrees of hole collapse, leakage, water gushing and leakage, gushing, collapse occurred at the same time.People to produce these complex conditions of the strata, collectively referred to as complex strata.According to relevant statistics, only about 30% of engineering meters occur in the geological drilling of complex strata, while the engineering cost to complete these engineering quantities accounts for more than 60% of the total engineering cost, and more than 95% of engineering quantities discarded due to accidents occur in the drilling of these complex strata.Further analysis of the reasons, it is not difficult to see that these distressing scrap amount, and most of it is due to drilling in complex strata, the hole protection technology can not keep up.
The hole protection technology of complex stratum
1. In the process of drilling, unstable strata often encounter collapse and dropping of blocks inside the hole, as well as various degrees of encounter with resistance, stuck drilling, buried drilling accidents, borehole shrinkage and oversize, etc., which are collectively referred to as unstable strata.Unstable formation dynamic unstable formation and water sensitive unstable formation.
1.1 mechanical unstable stratum: refers to the multidirectional compression caused by geological origin or tectonic movement.The force inside the stratum is unbalanced, and once drilled through, the original equilibrium state is destroyed. In addition, unstable collapse and dropping of the hole wall are caused by gravity.For example, the 5 boreholes we drilled in no.56 mining area of jinchuan company belong to this geological feature, with 0 ~ 15m miscellaneous fill, 15 ~ 35m gravel layer, 35 ~ 55m gravel sand layer and 55 ~ 80m gneiss diorite. It is not difficult to see from the above that 55m is a mechanically unstable stratum before.To deal with this kind of stratum, we use the traditional mud as soon as we open the hole, adjust the consistency to make it reach the flow plastic state, and then use the screw pump which is good at transporting the mud to send the slurry to the drilling hole circulation, to ensure the drilling construction, this hole protection technology can basically complete the hole protection requirements of this stratum;In the gravel layer with strict requirements for core mining, we used SM vegetable gum drilling fluid with a concentration of 4% and a viscosity of more than 300 seconds. The hole protection effect was good during drilling, and the "core" cemented into a column could be taken out.For the fractured zone deep in the formation, the drilling fluid with excellent performance is used to pass through the zone quickly on the principle of "less vibration, faster passing".If PHP with high molecular weight is used, the concentration is adjusted to 500 ~ 1000ppm. Under the condition of not running the pump, hole drilling is carried out. This special well protection fluid is used in the 280-300m hole section of zk56-3.
1.2 water-sensitive strata: the simple definition is that the rock strata on the pore wall are loose, soft, expanded and spalling due to hydrolysis and hydration caused by the intrusion of washing fluid. The strata with such phenomenon are called water-sensitive strata.For example, in the 170m ~ 185m hole section of the zk56-3 well in the second mining area of jinchuan company, the formation is seriously petrified of green mud, and the broken diorite between layers is largely cemented with clay. When drilling in this section, the borehole is obviously manifested as shrinkage, collapse and drilling swaddling, and the washing fluid is seriously infected.The most prominent feature of such strata is water resistance. Therefore, in the drilling process, the first step is to prevent free water from contacting or infecting these strata, so as to avoid hydration of the rock-soil surface of these strata.In addition, it is necessary to supplement and increase the ion concentration in the medium of the flushing solution, such as K+, Na+, Ca2+, etc., so as to make it balance with the ion concentration of water in the rock formation, prevent the infiltration and hydration of the rock formation, so as to facilitate the stability of the pore wall.Integrated the hydration mechanism of the water sensitivity formation, should let the drilling rinses have such two characteristics: one is water loss is small, the second is considerable ion concentration, we the special hole section of drilling and to formulate the corresponding countermeasures, will rinses and related treatment parameters have been adjusted: (1) choose efficient water loss, like potassium humate and modified starch PGS double agent;(2) choose quality flocculant, such as molecular weight in more than 3 million, 30% of the degree of hydrolysis of polyacrylamide PAM;(3) add the optimal inorganic salt, such as KCL anti-collapse.The specific parameters we selected were 1000ppmmPHP, 5% PGS and 5% potassium humate, supplemented with 2-5% KCL.In this section, basically played a "waterproof, hole protection" purpose.
2 gushing and leaking formation
For general lost formation, relatively easy to deal with, as long as in drilling, control the specific gravity of the flushing fluid and supplemented by inert materials or plugging slurry, can basically block the leakage channel.The zk56-3 hole in the second mining area of jinchuan company can be said to be full hole leakage. For the general leakage layer, we mainly use 801 plugging agent and high concentration PAM, supplemented by inert materials such as sawdust and sheep manure.To deal with the larger leakage hole section, the general use of grouting to plug, can be used to try a strong water resistance, quick setting performance of viscoelastic grouting mixture, in fact, the formula is: water cement ratio of 0.5 ordinary Portland cement, 3% calcium chloride, 1% concentration of the molecular weight of the unhydrolyzed in 300 ~ 600 104 PAM aqueous solution.For the stratum with both leakage and surge, it costs money and time to treat with chemical well cleaning fluid, and the effect is not very ideal, so in the construction of zk56-3 hole, we used the traditional mud hole protection technology to quickly pass through the gushing and leaking layer, and then run the casing to isolate, the effect is good.
Three conclusions
When core drilling is carried out in complex strata, it is necessary to give priority to technological design and scientific construction.For unstable strata, the combination of traditional mud and chemical flushing liquid with scientific formula is used for hole protection.The traditional hole protection technology of mud and casing isolation should be emphasized in the formation with gushing and leaking.
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