US3072192A - Method of inhibiting corrosion in oil production - Google Patents

Description

United States Patent Ofllice 3,072,192 Patented Jan. 8, 1963 3,072,192 METHOD OF INHIBITING CORROSION IN OIL PRODUCTION Hendrik K. Van Poollen, Littleton, Colo., assignor t Marathon Oil Company, a corporation of Ohio No Drawing. Filed Feb. 19, 1959, Ser. No. 794,255 6 Claims. (Cl. 16642) My invention relates to methods for preventing or reducing corrosive effects on oil well equipment installed in or associated with producing oil wells.

This invention is useful in various types of producing wells but has particular application to treatments utilized in connection with oil well stimulation. The oil contains ingredients possessing highly corrosive properties which attack the metallic surfaces in the well equipment and surface installations through which the oil is conducted, treated and stored.

Among the methods utilized in oil well stimulations is a practice known as hydraulic fracturing or sand fracturing, in which a fluent body of sand in graded sizes is pumped or forced into an oil reservoir to render such formation more permeable and to promote flow of oil from the structure into the production well.

It has been known that corrosion inhibitor compositions, if released in the structure to flow with the oil, will retard the corrosive action to a considerable degree, and it is beneficial to have the inhibitor in place when pumping begins.

The present invention represents a departure from prior inhibition methods, in utilizing corrosion inhibitors which are in solid form, are substantially insoluble in the carrier fluid by which they are conducted into the formation, and go into solution slowly in the oil production of the well, which usually has a substantial water con-tent. The inhibitor composition may be water soluble or oil soluble and preferably is only slowly soluble in the formation fluids of the oil stream being conducted through the well. A suitable composition for this purpose is described in Rohrback et a1. Patent No. 2,6843 32, and the pellets may be formed to meet size specifications or reduced and sized to meet the size requirements of its intended use. A novel method is provided for distributing such compositions throughout the reservoir structure and corrosive action is inhibited for a relatively long period due to the slow rate of dissolution.

Accordingly it is an object of my invention to provide a simple, economical and eflicient method of inhibiting corrosion in metallic equipment utilized in oil production.

Another object of this invention is to provide a simple, economical and eflicient method of distributing a corrosion inhibiting composition in an oil producing structure and for retaining such composition in the structure for a relatively long period.

A further object of the invention is to provide for the distribution of a corrosion inhibiting composition throughout an oil bearing formation as an adjunct to a charge of material being distributed throughout the formation for other purposes.

A typical procedure according to the present invention is to form solid inhibitor chemicals as pellets which dissolve slowly in formation fluids. These pellets are sized and mixed with propping sand in the same size ranges until they are uniformly distributed in the sand. This mixture is utilized as the propping sand of a hydraulic fracturing treatment and is pumped into cracks away from the well bore. The pellets are slowly soluble in the formation fluids but supply a suificient inhibiting effect from the outset, and because the rate of dissolution is so slow, this effect persists for relatively long intervals.

Various compositions may be used as the inhibitor material, as for example, the class of compositions known as semi-polar organic corrosion inhibitors and inorganic compositions, such as sodium dichromate and sodium nitrite. In preferred practice these inhibitors are mixed with a suitable liquefied inert but slowly soluble material which will congeal in the pellet forming stage and can be controlled as to size so that the pellets are produced in the same size range as the propping sand. It is not necessary to have the inhibitor composition in solution prior to congealing so long as it disintegrates in the formation fluids and pellets formed of compressed solids also may be employed.

The quantity of pellets utilized in the treatment will vary with the amount of sand being used, the size of the fractured area being filled, and the productivity of the well. In many treatments where a considerable quantity of sand is being used, an addition of pellets in an amount approximating one percent by volume of the sand will be adequate under most conditions. Under extreme conditions as much as 10% might be required in such a mixture, but any amount in excess thereof appears to have no actual benefit and only adds to the cost of the treatment.

The sand-inhibitor mixture is distributed throughout the fractured area according to the usual hydraulic fracturing procedure. As soon as the sand distribution is completed pumping can begin and continues as long as required. The inhibitor commences functioning as pumping begins and continues in the same manner for a long interval providing substantially the same degree of corrosion control throughout the entire period.

In many instances it may be advantageous to introduce a substantial concentration of the inhibitor pellets into the formation preceding the introduction and distribution of propping sand, in order to push the inhibitor far into the formation. In such event, only a lean mixture of inhibitor in the sand will suflice, as the formation fluids will contain dissolved inhibitor on reaching the propping sand.

From the foregoing description it will be apparent that this invention may be practiced with a wide selection of chemicals as the inhibitor of the treatment, and the quantity of inhibitor used may vary substantially according to the requirements of a given treatment. Changes and modifications may be availed of within the spirit and scope of the invention as set forth in the hereunto appended claims.

I claim:

1. The method of inhibiting corrosion in oil production from hydrocarbon producing reservoir formations penetrated by a well, which comprises mixing a corrosion inhibitor composition in solidified pellet form with a propping agent in approximately the same size range, said pellets being substantially insoluble in a carrier fluid and at least slowly soluble in formation fluids, suspending the mixture of pellets and propping agent in said carrier fluid, delivering said mixture through a well bore to the bottom of said well, initiating a fracturing of said formation at the bottom of the well by increasing the pressure on said carrier fluid to a degree sufficient to lift the overburden and force said fluid mixture into the formation, whereby it is distributed through said formation outwardly from said well, and withdrawing formation fluids from the formation and through the well to induce a slow dissolution of the pellets by contact with the formation fluids until the inhibitor is completely dissolved therein.

2. The method of inhibiting corrosion in oil production from hydrocarbon producing reservoir formations penetrated by a well, which comprises mixing a corrosion inhibitor composition in congealed pellet form with a propping agent in approximately the same size range, said pellets being substantially insoluble in a carrier fluid and at least slowly soluble in formation fluids, suspending the mixture of pellets and propping agent in said carrier fluid, delivering said mixture through a well bore to the bottom of said well, initiating a hydraulic fracturing of said formation at the bottom of the well by increasing the pressure on said carrier fluid to a degree suflicient to lift the overburden and force said fluid mixture into the formation, whereby it is distributed through said formation outwardly from said well, and withdrawing formation fluids from the formation and through the well to induce a slow disolution of the pellets by contact with the formation fluids until the inhibitor is completely dissolved therein.

3. The method of inhibiting corrosion in oil production from hydrocarbon producing reservoir formations penetrated by a well, which comprises mixing a water soluble corrosion inhibitor composition in solidified pellet form with a propping agent in approximately the same size range, said pellets being substantially insoluble in a carrier fluid and at least slowly soluble in formation fluids, suspending the mixture of pellets and propping agent in said carrier fluid, delivering said mixture through a well bore to the bottom of said well, initiating a fracturing of said formation at the bottom of the Well by increasing the pressure on said carrier fluid to a degree suflicient to lift the overburden and force said fluid mix-ture into the formation, whereby it is distributed through said formation outwardly from said well, and withdrawing formation fluids from the formation and through the well to induce a slow dissolution of the pellets by contact with the formation fluids until the inhibitor is completely dissolved therein.

4. The method of inhibiting corrosion in oil production from hydrocarbon producing reservoir formations penetrated by a well, which comprises mixing an oil soluble corrosion inhibitor composition in solidified pellet form with a propping agent in approximately the same size range, said pellets being substantially insoluble in a carrier fluid and at least slowly soluble in formation fluids, suspending the mixture of pellets and propping agent in said carrier fluid, delivering said mixture through a well bore to the bottom of said well, initiating a fracturing of said formation at the bottom of the well by increasing the pressure on said carrier fluid to a degree suflicient to lift the overburden and force said fluid mixture into the formation, whereby it is distributed through said formation outwardly from said well, and withdrawing formation fluids from the formation and through the well to induce a slow dissolution of the pellets by contact with the formation fluids until the inhibitor is completely dissolved therein.

5. A method as defined in claim 1, in which the mixture of pellets and propping agent is in the proportion of 1 to 10% by volume of pellets in said agent.

6. A method as defined in claim 1, in which the mixture of pellets and propping agent is in the proportion of approximately 10% by volume of pellets in said agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,635,698 Rohrback et a1 Apr. 21, 1953 2,684,332 Rohrback et al. July 20, 1954 2,818,118 Dixon Dec. 31, 1957 2,877,180 Parks et a1. Mar. 10, 1959 2,891,619 Sneary June 23, 1959

Claims (1)

1. THE METHOD OF INHIBITING CORROSION IN OIL PRODUCTION FROM HYDROCARBON PRODUCING RESERVOIR FORMATIONS PENETRATED BY A WELL, WHICH COMPRISES MIXING A CORROSION INHIBITOR COMPOSITION IN SOLIDIFIED PELLET FORM WITH A PROPPING AGENT IN APPROXIMATELY THE SAME SIZE RANGE, SAID PELLETS BEING SUBSTANTIALLY INSOLUBLE IN A CARRIER FLUID AND AT LEAST SLOWLY SOLUBLE IN FORMATION FLUIDS, SUSPENDING THE MIXTURE OF PELLETS AND PROPPING AGENT IN SAID CARRIER FLUID, DELIVERING SAID MIXTURE THROUGH A WELL BORE TO THE BOTTOM OF SAID WELL, INITIATING A FRACTURING OF SAID FORMATION AT THE BOTTOM OF THE WELL BY INCREASING THE PRESSURE ON SAID CARRIER FLUID TO A DEGREE SUFFICIENT TO LIFT THE OVERBURDEN AND FORCE SAID FLUID MIXTURE INTO THE FORMATION, WHEREBY IT IS DISTRIBUTED THROUGH SAID FORMATION OUTWARDLY FROM SAID WELL, AND WITHDRAWING FORMATION FLUIDS FROM THE FORMATION AND THROUGH THE WELL TO INDUCE A SLOW DISSOLUTION OF THE PELLETS BY CONTACT WITH THE FORMATION FLUIDS UNTIL THE INHIBITOR IS COMPLETELY DISSOLVED THEREIN.