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De-claying reagent ALPHAGLIN-R
Designed to destroy (de-clay) clay particles by acting on the crystal lattice, as a result of which structural bonds are weakened and suppressed, leading to almost complete destruction of clay particles, depriving them of the ability to peptize and compact, which contributes to their removal from the pore space of the formation.
It is an excellent alternative to alkaline reagents, the use of which in shale reservoirs is impossible, due to the strong hydration of clays, which is associated with an increase in the interplanar distance of particles.
It is an excellent alternative to alkaline reagents, the use of which in shale reservoirs is impossible, due to the strong hydration of clays, which is associated with an increase in the interplanar distance of particles.
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One of the reasons for the decline in well performance is the interaction of clay minerals and water. The natural permeability of the formation depends on the granulometric composition of minerals, formation fluids, physicochemical composition and exists only until it is opened during drilling, and then the filtrate of the drilling fluid enters the formation, the amount and depth of penetration of which, among other things, is determined by pressure (repression) on formation in the process of opening.
The value of repression, based on fishery statistics, reaches 14-21 MPa. Simultaneously with the penetration into the formation, the filtrates of drilling fluids cause swelling of clay particles and are retained in the pore channels of the formation by capillary forces, and displacement becomes possible only with significant pressure drops, making it difficult for the formation fluid to move to the bottomhole zone of the well. With such high repressions, the depth of penetration of drilling mud filtrate can reach 10 meters or more.
This phenomenon is hydration, in which there are two mechanisms of water adsorption on clay particles: adsorption of monomolecular water layers on the plane of the crystal lattices of particles and osmotic swelling due to a high concentration of ions held by electrostatic forces at the surface of clay particles.
In the case of compaction of sedimentary rocks under the action of the layers of sedimentary rocks located above, the water adsorbed by clay particles is squeezed out together with the pore fluid, while the amount of remaining water directly depends on the type and proportion of clay minerals, the depth of immersion, the presence of exchangeable cations and several less significant factors. In the process of opening layers with clay deposits, dehydrated clay adsorbs water, increasing its volume and can at the same time provoke both blockage of pore channels and disturb the stability of the wellbore, which is manifested by the plastic flow of the rock, mainly consisting of sodium montmorillonite.
Similar phenomena can be caused by osmotic swelling of clays. Due to the surface dissociation of clay particles and the dissolution of salts from the surrounding rock, concentration gradients appear between water interacting with clay and pore water, introducing osmotic forces into hydration. Osmotic swelling manifests itself when the concentration of cations between the clay layers predominates over the concentration of cations in the bulk of the aqueous solution, due to which water is drawn into the space between the layers, the distance between the layers increases and diffuse parts of double electric layers appear.
In addition to the filtrate of drilling fluids, the solid phase also penetrates into the formation, which leads to its blockage. With a permeability of 0.36-0.62 μm², the maximum degree of clogging of pores in the near-wellbore region of the formation is achieved, which seriously complicates the washing out of filtrate and clay particles in the return flow from the formation to the well.
The value of repression, based on fishery statistics, reaches 14-21 MPa. Simultaneously with the penetration into the formation, the filtrates of drilling fluids cause swelling of clay particles and are retained in the pore channels of the formation by capillary forces, and displacement becomes possible only with significant pressure drops, making it difficult for the formation fluid to move to the bottomhole zone of the well. With such high repressions, the depth of penetration of drilling mud filtrate can reach 10 meters or more.
This phenomenon is hydration, in which there are two mechanisms of water adsorption on clay particles: adsorption of monomolecular water layers on the plane of the crystal lattices of particles and osmotic swelling due to a high concentration of ions held by electrostatic forces at the surface of clay particles.
In the case of compaction of sedimentary rocks under the action of the layers of sedimentary rocks located above, the water adsorbed by clay particles is squeezed out together with the pore fluid, while the amount of remaining water directly depends on the type and proportion of clay minerals, the depth of immersion, the presence of exchangeable cations and several less significant factors. In the process of opening layers with clay deposits, dehydrated clay adsorbs water, increasing its volume and can at the same time provoke both blockage of pore channels and disturb the stability of the wellbore, which is manifested by the plastic flow of the rock, mainly consisting of sodium montmorillonite.
Similar phenomena can be caused by osmotic swelling of clays. Due to the surface dissociation of clay particles and the dissolution of salts from the surrounding rock, concentration gradients appear between water interacting with clay and pore water, introducing osmotic forces into hydration. Osmotic swelling manifests itself when the concentration of cations between the clay layers predominates over the concentration of cations in the bulk of the aqueous solution, due to which water is drawn into the space between the layers, the distance between the layers increases and diffuse parts of double electric layers appear.
In addition to the filtrate of drilling fluids, the solid phase also penetrates into the formation, which leads to its blockage. With a permeability of 0.36-0.62 μm², the maximum degree of clogging of pores in the near-wellbore region of the formation is achieved, which seriously complicates the washing out of filtrate and clay particles in the return flow from the formation to the well.
There are three options for chemizing the bottomhole formation area to increase its permeability:
- 1Dissolution of clay particles by acid and clay acid treatments, which have an undesirable effect in the form of an effect on silicate cements, in addition to the effect on clay particles.
- 2Changing the exchange complex in order to prevent peptization of clay particles in the formation, for which aqueous solutions of electrolytes with the content of K + and NH₄ ions are used to prevent swelling of clay particles. In this case, the concentration of electrolytes in the solution should prevail over the concentration of electrolytes in formation water. It is better to use such compositions for well flushing.
- 3Destruction (de-claying) of clay particles by affecting the crystal lattice, weakening and inhibiting structural bonds, leading to almost complete destruction of clay particles, depriving them of the ability to peptize and compact, which contributes to their removal from the pore space of the formation.
As a result of pilot tests in clay-covered reservoirs, it was revealed:
- The use of alkaline solutions is unacceptable due to strong hydration of clays due to an increase in interplanar spacing in clay particles.
- Aqueous solutions based on sodium bisulfite and sulfide alkali did not give any results.
- Compositions based on hydrochloric acid and clay acid (a mixture of hydrochloric and hydrofluoric (hydrofluoric) acids) are more effective, which is explained by the mechanism of action in which they do not destroy the structure of clay particles, but dissolve clay and silicate formations, creating channels. The processing time in this case is limited to 4 hours due to the gelation of the reaction products. Such compositions are good for treating the near-wellbore area of the formation, for increasing its permeability, followed by deeply penetrating treatment with organic acids.
- ALPHAGLIN-R proved to be the most effective. For example, in shallow reservoirs with a developed system of fractures (can be obtained by periodic hydroswabbing), the permeability after treatment increases from 4 to 8.5 times. In conditions of mud clogging of the bottomhole formation zone with drilling mud, after the application of ALPHAGLIN-R, the permeability can increase from 3.8 to 5.6 times. For the treatments, an aqueous solution of ALPHAGLIN-R with a concentration of 6 to 10% was used.
Benefits of Application
ALPHAGLIN-R
ALPHAGLIN-R
- Multiple reduction in the need to attract workover and workover teams
- The composition does not contain liquid acids, which eliminates the need for storage tanks for acids and acid aggregates in field conditions
- Powder reagent - easy to transport and store
- It can be effective when completing wells that have come out of drilling