INNOVATIVE MUD ADDITIVES DEVELOPED FROM INDUSTRIAL WASTES

Alexander P. Zakharov
Rekiz
Moscow

Evgeny A. Konovalov, Yuri A. Ivanov
All-Russian Research & Development Geological Exploration Institute
Moscow

Laboratory studies and field tests of muds formulated with specialty chemicals made in part from industrial wastes and byproducts have proven ecologically safe and efficient as water-loss reducers, gelation agents, pH regulators, lubricants, thinners, and inhibitors.

Since the breakup of the U.S.S.R., most of the raw material deposits for producing drilling mud chemicals and many of the corresponding :'industrial facilities are now located beyond the Russian Federation borders. Additionally, the political change destroyed many of the long-term, stabilized contracts between enterprises, plants, and oil and gas production regions with much drilling activity. These changes resulted in a sharp drop in production of drilling mud chemicals and additives and a low supply for the Commonwealth of Independent States (C.I.S.) drilling and production enterprises. Not all of the enterprises have hard currency to buy mud products and chemical products from abroad; therefore, research into other practical sources for drilling chemicals has increased in the C.I.S.

Many new drilling and production joint ventures in the C.I.S. provide their own drilling mud chemicals and additives brought from abroad. This practice is rather costly, however, considering logistics and transportation expenses. It would be much more reasonable, both economically and technologically, for those joint ventures to use local drilling mud chemicals and additives already field-tested and proven environmentally safe.

Many of the raw material processing plants in the C.I.S. have huge amounts of industrial by-products and wastes resulting from a rather low level of existing production technology. For example, during the production of vitamins and synthetic aromatic substances, about 0.6-0.7 tons of industrial wastes are produced from each ton of initial raw materials. Moreover, those wastes and by-products contain significant quantities of various components useful for production of chemicals for treating drilling muds.

The regulations in the C.I.S. drilling industry are not as strict as those in the chemical, refining, and some other industries. Thus, environmentally safe industrial wastes and by-products can be used and experimented with on a rather large scale.

The first materials evaluated were readily available, abundant, and inexpensive industrial wastes with compositions suitable for use as gel-forming agents, alkali and lubricating agents, and rheology-controlling agents for bentonite drilling muds. Most of those chemicals are multifunctional; that is, they influence several drilling mud properties simultaneously. Additionally, some of the lab work investigated the various compositions of industrial wastes in special formulations for use as bridging and consolidating agents.

GEL-FORMING AGENTS

Sewage disposal sediments, such as sludge and cake, were investigated individually and in combination with conventional gel-forming agents such as bentonite, peat, and chalk. Based on the lab tests, the greatest potential is in the cake from sewage disposal plants for silicon-organic products. This type of cake includes quick-lime, carbonates, and phosphates of calcium and silica gel (Table 1).

Composite polymer-containing materials (starches) are also valuable gel-forming agents. One source is from biological material with expired storage dates (for their original uses), because their biological origin allows renewed activity under normal conditions. These agents do not pollute the environment, are nontoxic, and have long shelf lives for extended storage (1-1.5 years) for drilling purposes.

One of these gel-forming materials includes potato starch, sodium chloride, and surfactants; the material is called a combined starch agent (KRK, a Russian acronym). Because of the high starch content, this material is used in drilling through formations with high mineralization (Table 2).

The field tests of these gel-forming agents in Western Siberia and Kazakhstan confirmed the results of the laboratory studies. The silicon-organic gel-forming agent (KDS, a Russian acronym), at concentrations of 2-3 wt %, increased the gel rheological properties of bentonite and polymer nonbentonite drilling muds. The combined starch agent (KRK) maintained rated Theological and filtration properties at its concentration of 17-25 vol % in drilling mud. The combined starch agent also minimizes, or eliminates in some cases, the use of bentonite and water-loss additives like conventional starch or cellulose. Mixing these chemicals in a silicate water solution increases the gel-forming effect of the additives because it generates complex silicon-gel systems with high adsorption capacity.

ALKALI SALTS

In place of standard caustic and sodium alkalis, alkali-containing wastes from metallurgical, perfume, and microbiological industries were analyzed for use in drilling fluids. Other possible raw materials studied included melted alkali wastes from steel mills, alkali cellulose from chemical fiber production, basic alkali solutions, and salt cakes of fusion produced by vitamin and aromatic product plants.

To use water-based alkali salts and hydrocarbon industrial wastes, the materials are first burned, resulting in a cake of fusion, which is a solid material containing about 20-25% sodium carbonate and a mixture of chlorides and sulfates of sodium and calcium carbonate. One particular alkali cake of fusion (Russian abbreviation OShR) is a material containing up to 75% caustic soda and 15-20% sodium nitrate. This material is used for increasing the pH of bentonite muds; for mixing complex polymer chemicals like starch, lignin, and acrylate; and for producing sodium and silicate from silica gel (Table 1).

These materials have been used as a calcium-eliminating agent instead of sodium bicarbonate, in particular for drilling-out cement plugs in a well. Water solutions of these cakes have a pH

Table 1 shows another characteristic feature of the cake of fusion; even small amounts (about 0.05-0.10%) of this material can decrease the water loss of drilling mud. Using this material with borax allows the generation of silicates having better adhesion properties. These properties can be used during special operations for consolidation of sloughing formations in wells.

Alkali cellulose, containing up to 20-22% caustic soda and cellulose fibers, is useful as a bridging and gel-forming additive in drilling muds with low pH. This material is especially useful during drilling through mud-loss zones in carbonate formations. Table 3 shows how the alkali cellulose influences drilling mud properties.

These alkali materials and additives have been field tested successfully during operations in the Komi Republic, Eastern Siberia, Kazakhstan, Orenburg, and the Tyumen area.

POLYMERS AND LUBRICANTS

Large volumes of unused industrial wastes from hydrolysis plants have potential in the production of lignosulfonates and similar chemicals. With about 30 hydrolysis process plants in the Russian Federation, this potential volume of raw materials is of interest to the drilling industry. These polymer wastes consist of residues from yeast production (Russian abbreviation PDO).

Table 3 shows the analysis of muds using these types of wastes. These chemical additives decrease water loss of bentonite drill muds and regulate their rheology properties.

By-products of vegetable oils such as sunflower, soy bean, and mustard have applications as ecologically safe lubricating additives. Previous lab work and field tests indicated that wastes from sunflower oil manufacturing were effective and economical as mud lubricants. Recent laboratory work has shown that derivatives of mustard oil wastes (from vitamin plants) have applications as mud lubricants. The soapstocks produced as industrial wastes at margarine plants can be also used as raw materials for production of ecologically safe drilling mud lubricants.

SILICON-GEL CHEMICALS

Silicates and combined silicon-based chemicals (concentrates) used as inhibitors, bridging agents, and consolidating agents can be based on silica gel, which is available as industrial wastes from fertilizer and alkali production.

Composite silica gel chemicals can be formulated with specific, predetermined properties by mixing active additives to the silica gel solution at particular stages of the solution process. The active additives mentioned above are recommended in particular as cross-linking materials during production of dry powder or brick-solid multipurpose chemicals. These chemicals can be used successfully to adjust rheological and water-loss properties of drilling muds.

Sodium silicate, the main cross-linking component of these drilling mud concentrates, can be produced at any industrial enterprise by a nonautoclave method. The silica gel for this process can be obtained from a number of fertilizer plants. Many peat-producing factories are located in the vicinity of intensive drilling operations in the C.I.S., making them very attractive as suppliers of raw material for manufacturing composite mud chemicals.

Sapropel is produced during the removal of bottom sediments from ponds and lakes mainly in central Asia. This ecologically safe material is normally used as an agricultural fertilizer but can also be used for production of composite mud chemicals. The sapropel reserves in Russia are huge.

Fine-grained materials, such as peat and sapropel, have a high adsorption activity for heavy metal ions. Thus, they are well-suited for use with sewage waters and sediments containing hydroxides of copper, chromium, zinc, aluminum, and others that are environmentally dangerous as pure metals.

The components for controlling water-loss and rheological properties in the composite chemicals can be such materials as sodium poly . phosphate, lignosulfonate, water-soluble cellulose ethers, acrylates, and alkali-rich industrial wastes (sewage water). The gel-forming agents for sodium or potassium silicates can be either conventional materials or unconventional materials such as acids, salts, polymers, sapropel, or activated coal from industrial waste sources.

The chemicals, additives, and materials described herein have been tested in the field already. Some new products are still undergoing testing in laboratories and in the field, and other raw materials are being investigated for versatility and ecological safety.

BIBLIOGRAPHY

Konovalov, E.A., et al., "Silicate Hydrogel Drilling Muds and Chemicals for Well Drilling," Information Review of the Scientific-Technical Achievements and Modem Experience in Geology and Exploration of Resources, Moscow, No. 5, 1991, pp. 53-64.
Konovalov, E.A., Shabanova, N.A., Silos, I.Y., and Zakharov, A.P., "Boron-Silicate Reagents for Drilling Oil and Gas Wells," the Fourth Symposium on Mining Chemistry, MinGhem '92, Kiev, Ukraine, Oct. 6-9, 1992.
Zakharov, A.P., and Konovalov, E.A., "Silicon-Based Additives Improve Mud Rheology," OGJ, Aug. 10, 1992, pp. 61-64.
Zakharov, A.P., et al., "Method of Drilling Mud Formulation," authorship certificate of Russia No. 1699991, priority date July 10, 1989, registration date Aug. 22, 1991.
Konovalov, E.A., et al., "Complex Chemical for Drilling Mud Treatment and Method of Its Formulation," Russia patent No. 1790591, priority date April 23, 1991, registration date Sept. 22, 1992.
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