Polyanionic cellulose

Polyanionic cellulose sodium salt (PAC) is a white or slightly yellow powder, non-toxic and odorless, it can be dissolved in water, has good heat stability and salt resistance, strong antibacterial properties, low viscosity PAC is a A high-quality, low-molecular-weight, low-viscosity cellulose polymer. High-viscosity PAC is a high-quality, high-molecular-weight, high-viscosity cellulose polymer. The mud fluid prepared with the product has good water loss reduction, suppression, and high temperature resistance. Widely used in oil drilling, especially brine wells and offshore oil drilling.

 I. Application in engineering fields such as oil and gas drilling and well digging

     Drilling fluid and completion fluid technology is an important part of oil well engineering. It plays a key role in ensuring safe, high-quality and fast drilling. As a kind of treatment agent used to adjust the properties of drilling fluids and completion fluids, the main role of cellulose derivatives is to reflect the aspects of filtration loss and viscosity increase.

     It is generally believed that the mechanism of polyanionic cellulose to reduce filtration loss is mainly to improve the coalescence stability of the system by forming an adsorption solvation layer on the surface of the drilling fluid clay particles, and to prevent the clay fine particles from becoming larger by protecting the clay particles ; Reduce the permeability of mud cake by increasing the viscosity of the filtrate and plugging.

  Polyanionic cellulose is easily dispersed in all water-based drilling fluids, and can be used from fresh water to saturated brine drilling fluids. In low solid phase and non-existent phase drilling fluid, it can significantly reduce the amount of filtration loss and thin mud cake thickness, and has a strong inhibitory effect on shale hydration. Compared with the CMC produced by conventional processes, PAC has the following characteristics:

    a. High degree of substitution, uniform replacement, high transparency, controllable viscosity and precipitation loss;

    b. Any water-based mud suitable for fresh water, sea water or saturated salt water;

    c. The mud prepared with this product has good properties of reducing water loss, feasibility and high temperature resistance;

    d. The mud prepared with this product has rheological properties,

    E. Can inhibit the dispersion and expansion of clay and shale in high-salt media, so that the pollution of the well wall can be controlled;

    F. Stabilize the soft soil structure to prevent the collapse of the well wall caused by the rising water level;

    G. Slow down the accumulation of drilling solids in the mud when the well is drilling through the rock surface;

    H. Suppress the turbulence in the drill pipe and keep the return system to a minimum pressure loss;

    I. Enabling mud to increase pulping volume and reduce filtration loss;

    P. Can stabilize mud foam.

  Therefore, PAC is ideal as an inhibitor and fluid loss reducing agent. The mud main fluid prepared by PAC can inhibit the dispersion and expansion of clay and shale in a high-salt medium (monovalent salt), and control the pollution of the well wall. In addition, the use of PAC to configure the mud workover fluid is low-solid phase, so that the permeability of production is prevented by solids, that is, the production layer is not damaged; Less, can avoid the formation of water ballast due to the blockage of the emulsion due to the ingress of water. It can avoid the permanent destruction of the production layer and has the ability to carry the clean wellbore.

  The more uniform the distribution of the substituents of the product after cellulose carboxymethylation, the CH2OONa group, on the glucose ring group, the more structural units on the entire macromolecular chain are easy to hydrate, and the counterions in the mud react with The less the charge neutralization effect of the polyion of the product after the basicization, the greater the degree of expansion of the macromolecular chain, the more favorable the hydration, and the protective effect on the mud. Polyanionic cellulose PAC has uniform substitution, good temperature and salt resistance, stable viscosity in complex environments, high water loss control ability, can control the rheology of drilling fluid for a long time, and give full play to its proper function. In general, the greater the degree of substitution of the product, the more uniform the distribution, and the larger the molecule can expand in solution, the better it is for hydrating the water, and it is also more beneficial for improving its protective effect on the mud. Low-viscosity PACs are commonly used to reduce water loss and viscosity-reducing agents. The PAC was measured according to the method of measuring the loss of water by the API loss meter. The API dehydration meter was used for testing at a pressure of 0.7Mpa. (Table 1)

Second, the characteristics of polyanionic cellulose sodium salt (PAC)

   (1) Suitable for any mud from fresh water to saturated brine

   (2) The low-viscosity PAC can effectively reduce the amount of filtration loss, and does not significantly increase the system mucus, especially the high solid content system.

   (3) The glutinous PAC has a high pulp production and a significant effect of reducing filtration loss. It is especially suitable for low solid phase mud and non-solid phase salt cement slurry.

   (4) Mud fluid prepared by PAC can inhibit the dispersion and expansion of clay and shale in a high salt medium, so that the pollution of the well wall can be controlled.

   (5) Excellent mud drilling fluids and workover fluids are also highly effective fracturing fluids.

Application of Polyanionic Cellulose Sodium (PAC)

   (1) Application of PAC in drilling fluid

   PAC is ideal as an inhibitor and fluid loss reducing agent. Mud fluids formulated by PAC can inhibit the dispersion and expansion of clay and shale in high-salt media, thereby controlling well wall pollution. Because PAC has better reaction uniformity, higher degree of substitution, better transparency, better salt resistance and heat resistance than CMC, the higher pulping capacity (PAC-HV) and lower water loss ( PAC-LV).

(2) Application of PAC in workover fluid

The workover fluid prepared with PAC is low solid phase, it will not block the permeability of the production layer due to solids, and will not damage the production layer; and it has a low water loss, which is the decrease in the amount of water entering the production layer and the water Water ballasting can occur due to emulsion blockage.

Workover fluids formulated with PAC provide advantages not available in other workover fluids;

Protect the production floor from permanent damage;

Possess the carrying ability of clean wellbore, and the workload of maintaining wellbore is reduced;

Resistant to infiltration of water and sediment, and rarely foam

It can be stored or transferred from well to well, and the cost is lower than ordinary mud workover fluid;

   (3) The role of PAC in fracturing fluid

    The fracturing fluid prepared with PAC is resistant to 2% KCL solution (must be added when preparing fracturing fluid) and has good solubility. It is easy to use, can be prepared on site, and has fast gelling speed and strong sand carrying ability. Used in formations with low osmotic pressure, its fracturing effect is more excellent.