US3491835A - Recovering,desalting,and transporting heavy crude oils - Google Patents

Description

Jan. 27, 1970 RECQVERIIWJ,` DESALTING, AND TRANSPORTING HEAVY CRUDE OILS Filed Deo. 29. 1967 MAKE-UP MAKE-UP D. W. GAGLE 'Rs REFER-EME SEARCH ROOM U.S. Cl. 166--305 10 Claims ABSTRACT OF THE DISCLOSURE A process for transporting asphaltic crude oils in which the asphaltic crude oil is emulsitied at the well location, or at a central ptijmping station by an emulsitiyingagent and water, and transported through a pipeline to adestination point. The, emulsion is then broken which results in desalting the oil, and the crude oil separated from the emulsifying agentand water. The separated emulsier and water are then recycled through the same or another pipeline, and therecycled emulsifying agent and water are utilized to emulsify additional crude oil, and/or to aid in the recovery of crude oil from the oil bearing formation.

This invention relates to a method of processing asphaltic base crude oils for transporting the highly viscous essentially non-puiripable oils through a pipeline for long distances. In another aspect, it relates to the conservation of emulsifying agent utilized to emulsify the crude oil and to aid in recovery of the oil by recycle of the agent from the destination point to the well location. In a further aspect, itrelates to a method of economically desalting asphalticbase crude oils while at the same rtime facilitating the t'fnsfer of the heavy crude oils from the well location to fail-destination point and recovery of the heavy crude oil frpm the oil bearing formations.

In various locations throughout the world, oil deposits have been found which are so highly viscous at ambient temperatures so as to be non-flowing. Such crude oils cause many problems associated with the handling of these oils, not the least of which is transportation from well locations to processing plants, recovery of the oil from oil bearing formations, and desalting of the oil to render it market able. Conventional methods of desalting such as by elec tric desalters, are not feasible because of the high viscosity of the oil. Various methods of recovery of the oil from the oil bearing formation, such as combustion, forced steam, and conventional Water ood are at best only partially effective in removing the crude oil from the formation.

Two methods have been developed to transport asphaltic type crude oils, each of which has presented problems of economics. One method is to heat the crude oil until it reaches a fluid state, and then pump the oil through a pipe-1 line. However, such a method requires that the oil be maintained at a suticient temperature vto remain fluid, which requires heating of the oil at various points along the pipeline. When transportation is required over long distances, such an operation becomes prohitively experiu sive as more heating units are required along 'the line.

The other method which has been developed to handle highly viscous crude oils comprises emulsifying the oil are with water and various emulsifying agents. Such a treatment of the crude oil renders it sufficiently iiuid so that it may be pumped over long distances at ambient temperatures. At the point of destination, the crude oil emulsion is physically or chemically broken, and the crude oil separated and recovered for further processing. However, when large volumes of asphaltic crude oil require transportation, the cost of 'the emulsifying agents becomes prohibitive.

We have discovered a process whereby-highly viscous crude oils may be more economically recovered,ltransported over long distances, and desaltedltol render the crude oil marketable. Broadly, the invention resides in the`emulsifying of the "crude oil at the well head or a central pumping station with a surfactant, pumping the emulsion to the point of destination, breaking the emulsion in such a way as to preserve the chemical and physical properties of the surfactant and to desalt the crude oil, and returning the separated surfactant to the well location or central pumping station in the same pipeline, or in` another pipeline. Some of the recycled emulsier can advantageously be pumped into the oil bearing formation to aid in recovery of the oil.

Accordingly, it is an object of this invention to provide an improved system for recovery, desalting, and transportation of asphaltic base crude oils. It is another object of this invention'to provide a process whereby large volumes o f asphaltic ciude oils can be recovered, transported, and desalted more economically than by convertn tional methods.

Various other objects, advantages and features of the invention will become/apparent from the following deu tailed description and the accompanyingkirawing wherein:

FIGURE 1 of the drawing is a schematic ow diagram iluustrating the processfof the inventionshowng the varous steps of the processat a central pumping station and the destination point, and the pipelines connecting the two locations. FIGURES 2 and 3 of the drawing schematically illustrate preferred embodiments of the invention.

The crude oils which are employed ,according to the process of the invention include those crude oils which have such a high viscosity at ambient temperatures as to be substantially non-huid. Such crude oils are generally referred to as heavy asphaltic base crude oil or heavy asphaltic crude oil. Asphaltic base crude oils are found in various deposits throughout the world, examples being the Monagas Zone II crude oil found in Venezuela, Hamilt0n Dome and Oregon Basin crude oils of Wyoming, and the Kern River crude oil of California. Transportation of they crude oil over short distances and storage of the oil can be accomplished by heating the oil to maintain it in a fluid and pumpable state. However, in accordance with the invention, it is desirable to transport the crude oil as an emulsion from the well head directly to a central pumping station.

The type of emulsifying agents employed according to the process of the invention include chemical reagents which are commonly classed as anionic, cationic, and nonionic. These emulsifying agents are also called surfactants. Examples of the cationic and nonionic vagents which may be employed in the process of the invention are disclosed in U.S. Patent 3,345,193, Pitchford, issued Oct. 3, 1967. Anionic emulsifying agents have been known in the art for years and may also be employed,

In particular, commercially available agents maybe employed, an example being a polyoxyethylated alkylphenol, Triton X-305. Generally, the nonionic emulsifying agents employed` in accordance withthe process of the invention have` a formula as follows:

where R is selected from the group consisting of hydrogen, aryl and alkaryl radicals; and x, y and z are integers, such that (l) when x is zero, y is also zero, z is in the range of to 60, inclusive, and said R is one of said aryl and alkaryl radicals, and (2) when x and y are greater `than zero, the sum of x and z is in the range of 50 to 350, inclusive, and y is in the range of 40 to 60, inclusive.

The choice of the particular surfactant utilized will depend -upon various factors, including the nature of the crude oil, economics, and the like. Generally, however, it is preferred that the agent form an emulsion which is tight enough so as not to break during transportation, but which may easily be brokenat the point of destination to desalt the crude oil.

It is necessary in .practicing the invention that the emulsifying agent be susceptible to recovery from the breaking step of the process in a chemical and physical state which permits its reuse at the well location. Therefore, the nonionic s-nrfactant is preferred over the anionic or cationic agents in that the nonionic agent forms an emulsion which is easier to break and is easier to` recover in a form which may be returned to the well location. However, both cationic and anionic type emulsions are susceptible to a breaking step which results in recovery of the surfactant.

The amount of water utilized to form the emulsion will also vary according to the type of asphaltic crude utilized,

Moreover, it is essential that the emulsifying agent and water mixture, sometimes called a soap solution, be vigorously intermixed with the' crude oil in order to disperse the oil throughout the soap solution to form the emulsion. Various pumps are suitable for this purpose, one being a centrifugal pump. One preferred method isto f orm the emulsion in a colloid mill which is mounted on skids and can be easily transported to the oil storage facilities which are located near producing well locations. Another preferred method is to use the so-called pressure drop emulsiication process, wherein the mixtures of soap and oil are pumped through a narrow orifice which establishes the emulsion. Thus, the oily may be emulsilied at a storage facility or well head and then transported by truck or line to the central pumping station for pumping to the destination point.

At the well location, certain amounts of the recycled surfactant solution can be introduced into the well formation to aid in recovery of the crude oil. The elects of various surfactants upon the oil bearing strata of the formation are well known and are not repeatedhere for the sake of brevity and understanding. Generally, the surfactant causes a detergent action upon the entrained crude oil, loosen'mg it, and forcing it toward the surface. Generally, at least one well in the formation will be utilized as an input well for the surfactant.

Methods of injecting surfactant into an input well of an oil bearing formation are well known in the art. Such methods as additive water ood or steamooding are particularly suited for this purpose.

If the recycled surfactant is used to aid in recovery of the crude oil then a certain amount of the surfactant appears in the crude oil when it is removed from the outputwell head. As previously mentioned, it is within the scope of the invention that the crude oil emulsion be prepared at each output well location. The amount of makeup water and surfactant needed to establish the emulsion can be varied according to the amount of agent and forn mation brine being removed from the well head. Thus, if the' emulsion is established at each output Well head, it can be pumped to the central pumping station for transportation through the long distance line. The system may be optimized in that as more soap solution becomes associated with the crude oil at the output well head, the

amount of makeup emulsifying agent: and water needed' to establish the emulsion decreases. Economic benefit derived 'from utilizing recycled soap solution to both emulsify the crude oil for transportation and to aid in recovery of the oil is substantial.

In order to preserve the chemical and physical properties of the emulsifying agent, physical breaking of the emulsion is preferred over a chemical breaking of the emulsion. Generally, any type of gravity breaking may be employed; however, a forced gravity breaking of the emulsion is preferred, i.e., centrifugation. In addition, if any inorganic salts are present in the lcrude oil breaking of the emulsion results in the salt present in the oil being carried into the separated emulsifying agent and water mixture. Therefore, the crude oil is desalted as a result of breaking the emulsion which is essential to render the oil marketable.

In order to prevent the accumulation of the inorganic salts within the aqueous surfactant solution, a certain amount of the surfactant must be removed from the system prior to recycle of the surfactant to the well location or central pumping station. Such a procedure is conventionally known as a blow down operation. A sufcient amount of surfactant solution must be removed which results in the elimination of an amount of salt approximately equal to that amount of salt which is present in the crude oil and additive makeup water introduced to the system at the well location or the central pumping station. As a result, the amount of salt present in the recycle surfactant solution remains relatively constant.

In accordance with the invention, the` emulsifying agent is returned to the well head location or the central pumping station for reuse. The recycled agent can be returned in the ,crude oil emulsion pipeline if acontinuous process of recycle is not considered necessary..` If a continuous return of surfactant is desired, the surfactant can be returned` in another pipeline which is smaller in diameter than the crude oil emulsion line. Moreover, if desired, the separated surfactant can be concentrated by evaporation, or other suitable methods, and returned to the central station or well location by means of tank trucks, railroad tank cars, and the like.

Referring to the drawing, FIGURE. 1 is a schematic ow diagram which illustrates the invention. The apparatus associated with pump 7 and tank 2 are located at a central pumping station. Makeup water and makeup emulsifying agent enter tank 2 through lines 11 and 12 respectively. Makeup surfactant solution is mixed and heatedd in tank 2. The surfactant solution then passes through line 24, heater 26, and valve 53 into line 10. In line 10 crude oil which has been transported from various output well locations passes through line 21 and is associated with surfactant from line 24. The mixture passes through valve 41 into pump 7 wherein the centrifugal action of pump 7 establishes the emulsion. To aid in establishing the emulsion a certain amaunt of the mixture may be passed through valve 42 into line 29 through valve 44 and returned to line 10.

In accordance with the invention, the established emulsion is .pumped through long distance pipeline 27, through valve 46, and heater 31 into tank 3. Tank 3 and centrifuge 4 are located at the destination point. Intermediate pumping stations along line 27 aid in maintaining pressure in line 27 to aid in moving the emulsion to the destination point. yAs has been mentioned previously, no heaters are required along line 27 to heat the oil. The emulsion in tank 3 is {maintained at a constant temperature, and passes through line 33 into centrifuge 4. rlhe force exerted upon the emulsion by the action of centrifuge 4 results in a breaking of the emulsion. Desalted oil is removed from centrifuge 4 by line 16 and is stored for shipment, further processing, andthe like. A portion of the aqueous surfactant solution, which contains salt dissolved therein, passes into line through valve 47 and exists the system accordance with the blow down procedures which was discussed previously. The remaining sul-facu tant solution passes into line 34 through valve 48, and into collecting tank 5.

If line 27 is to be utilized to transport the surfactant solution back to the central pumping station, the flow of crude. oil emulsion through line 27 is halted and line 27 is pumped as free of emulsion as is possible. The surfactant solution in tank 5 is then passed through line 35, into pump'u'6, and forced by pump 6 through line 36, valve 49, into `,long distance line 27, andfreturned to the central pumping station. At the pumping station, any residual emulsion present in line 27 may be stored in a collecting tank;(not shown) until the returning surfactant solution has been completely returned. The returning surfactant solution is passed into line 14, through valve 45, and then into tank 2. The returned surfactant is then utilized along withadditional makeup water and makeup emulsifying agent't'o further emulsfy additional crude oil in line 10.

If, however, it is more desirable because of economic considerations to pump the emulsion continuously from the central pumping station to lthe destination point, an

.alternative process of the invention can be employed. In

such a case, the returning surfactant solution is pumped through a secondary pipeline 30, which is smaller in diameter than line 27, from line 35 to connect with line 14. Valves 50 and 51 located in line 30 regulate theow of surfactant solution therein. Accordingly, the surfactantfltnfay be returned at a rate siiicient to allow the f0rmatifof emulsion in pump 7.\l ,-1

In addition, in accordance withthe invention, a certain amount' of the oil may be passed into line 20 through valve 52 and passed to the various input wells in order to force the surfactant into the oil bearing formation along with water or steam to aid in recovery of the oil.

Moreover, an alternative process of forming the emulsion in accordance with the invention can be employed wherein the emulsion is established at each output Well head location. If such an alternative .process is employed, the returning surfactant passes from collectingv tank 2 through lines 24 and 20 to the output well locations.

FIGURE 2 of the irawing schematically illustrates the process of the inventipn wherein the returned surfactant solution is utilized to aid in the recovery of the crude oil from the oil bearing formation. An input well 61 is provided with a water or steam input line ,64, wherein water or steam is forced by pressure into the oil bearing formation. As previously mentioned, the recovery process in volves conventionally known methods of water or steam recovery vfrom oil bearing strata. To aid in loosening the crude oil from the formation, recycled surfactant passes from line into hold or surge tank 62. From tank 62, the surfactant passes through line 63 into input well 61, and is forced by the pressure exerted upon the water or the steam into the oil bearing formation.

FIGURE 3 of the drawing schematically illustrates a further embodiment of the invention wherein an input well 66 is provided with a recovery line 69. If surfactant solution is used to aid in recovery of the oil by injection through an input well as illustrated in FIGURE 2, certain amounts of the surfactant will appearalong with the crude oil and formation brine in line 69. If the emulsion is to be established at the central pumping'station, the oil is passed directly from line 69 into line 10 as illustrated in FIGURE 1. The amount of surfactant solution added to the crude oil in line 10 through line 24 as shown in FIGURE l will depend upon the amount of surfactant which is present in the crude oil which is removed from the output well 66.

Furthermore, in accordance with the invention, it may be desirable to emulsfy the crude oil at each output Well location because of the fact that the amount of formation brine present in the crude oil will vary depending on the location of the output well. Accordingly, surfactant solution is passed through line 20 into hold or surge tank 67 located at the output well location and illustrated in FIG URE 3. surfactant solution then passes through line 68 into line 69, the amount passed through line 68 being ad justed in accordance with the amount of formation brine present in the -crude oil and the amount of surfactant which is removed from output Well 66. The crude oil surfactant mixture then passes to an emulsifying means 71 wherein the emulsion is established. The emulsion then passes into line 10 and is pumped by pump 7 located in line 10 to the central pumping station as illustrated in FIGURE l.

As discussed previously, emulsifying means 71 may be a colloid mill mounted on skids, a pressure drop emulsilier unit, or acentrifugal pump. By the operation of the system illustrated above,l use of the emulsifying agent to aid in recovery, transportation, and desaltng of the asphaltic base crude oil results in a more eicient and economic process for handling the highly viscous crude oil. It can be seen that the alternative methods of operation of the system result in an optimization of the use of the expensive surfactant solution so that a minimum amount of the surfactant is utilized to solve the problems of handling the viscous oils. Moreover, by successfully eliminating the need for expensive heating equipment along the transportation route of the oil, a substantial savings in capital investment and operating costs are realized.

Certain other pumps, valves, gauges and other plumbing apparatus actually needed to operate the process of the invention have been intentionally omitted. Only sufcient hardware necessary to illustrate the invention have been shown.

A more comprehensive understanding, of my invention can be gained from the following illustrative example which, however, is not intended to limit the scope of the invention.

EXAMPLE In accordance with the process of the invention, a MonagasZone II crude ol of Venezuela is transported from the well location in the state of Monagas to a destination point on the coast.' The transportation 'system is schematically shown in the drawing. The Monagas Zone II crude is an asphaltic base oil with an API gravity at 60 F. of 9.2. The crude oil is brought to the surface by standard oil recovery techniques for asphaltic base crude oils; in the case of the Monagas crude, at a temperature of 190 F. The temperature of the liquids in lines 10, 11, and 14-16 is 190 F. The composition of the liquids in these lines is summarized in Table I. .I

Table l shows that salt enters the system in the makeup water and s formation brine in the crude oil. It also shows that gallons of surfactant solution are utilized to emulsfy 250 gallons of oil. The material balances showing the amount of emulsifying agent present in lines 14 and 15 is based upon the requirement that 2000 pounds of agent is needed to' emulsfy 250 barrels of Monagas Zone Il crude oil.

7 The emulsifying agent utilized is a commercially available liquid Triton X-305 which is a ypolyoxyethylated alliylphenol having the following formula:

phase and an aqueous phase; (4) separating said aqueous phase from said oil phase; and returning a portion of said aqueous phase containing said emulsifying agent to said rst point for reuse in step (1).

H CH3 CH3 /C 2. A process according to claim 1 wherein said aqueous CHVJPCHV C/ \C O (CH2CHZO)H H 5 phase containing said emulsifying agent which is returned H H to said first point is introduced into the oil bearing forma- H a H tion of said crude oil to aid in the recovery of said crude C oil which is utilized in step (l). H 3. A process according to claim 1 wherein step (5) is h 't ffr 25-35 nd r 3010 W ereln fl 1S all 1H egel 0 0In a 'l ave ages accomplished by returning the aqueous phase containing TABLE I Monagas M Dzmtl onagas esa e Water Ree cle Blow Down Zone I I Crude Make-Up Wter 0r Crude Oil Product (River Water) Solution Waste Water Emulsion Feed Line 10 Line 16 Line 11 Line 14 Line 15 Product Barrels/hour *250 230 10 12 Saybolt furol viscosity at 190 F., o 30 380 see 280 260 Salt (NaCl), pounds/1,000 barrels- 9570 API gravity, (60 F.) Salt (NaCl), grains/gallon Salt (NaCl), wt. percent Emulsifying agent, pounds/hour- Oil content Volume percent oil e Volume percent total Water 34 *Includes formation brine.

The crude oil emulsion is pumped at a flow rate of 380 barrels per hour from the well location to the coast and includes 230 barrels per hour of oil and 150 barrels per hour of water, of which barrels per hour of water is formation brine. The aqueous emulsifying agent is returned from the coast to the well location at a rate of 120 barrels per hour. If desired, the rate of return of the emulsifying additive can be greatly increased. The flow rates and compositions of the various streams are sumniarized in Table II.

TABLE II Recycle Make-Up Make-Up Aqueous Raw Oil Water Additive Solution Waste Water Desalted Oil Component Line 10 Line 11 Line 12 Line 14 Line 15 Line 16 Oil, b/h l Trace Trace 5 230 Water, b/h 2 3 120 2 3 30 Trace NaCl, ift/hr.2 (8, 792) (2, 19S) (2) Emulsifyng agent, #/hr (960) (240) (800) Total, b/h 250 10 120 30 230 l B lh. is barrels per hour.

2 Contains salt in solution.

5 Contains additive in solution. 4 #/hr. is pounds per hour.

Table II illustrates that when the emulsion is broken by the action of centrifuge 4, 230 barrels per hour of Monagas Zone II crude oil are recovered which contains only 2 pounds per hour of salt and 800 pounds per hour of emulsifying agent. The 800 pounds of additive represents about 2 percent by volume of the oil, and does not present a problem when the oil is processed since it is easily removed by fractionation. In addition, Table II shows that 240 pounds per hour of the emulsifying agent are lost in the blow down operation, but 960 pounds per hour of the agent, almost one half of the 2000 pounds per hour needed to emulsify the crude oil, is recycled for reuse. Therefore, a substantial savings in the cost of the emulsifying agent is realized.

Reasonable variation and modification will be apparent from a study of the disclosure, drawing and the appended claims.

I claim:

1. A process for transporting and desalting an asphaltic nase crude oil which is non-pumpable at ambient temperatures which comprises the steps of (l) emulsifying said crude oil at a first point with a mixture of an emulsifying agent comprising a nonionic or cationic surfactant and water to form an-oil-in-Water emulsion; (2) pumping said emulsion through a pipeline from saidI rst point a second point; (3) physically breaking said emulsion into an oil 6. A process according to claim 1 wherein the emulsifying agent is a nonionic surfactant.

7. A process according to claim 1 wherein the emulsifying agent is a cationic surfactant.

8. A process according to claim 1 wherein the physical breaking is accomplished by centrifuging the emulsion.

9. A process for recovering, transporting, and desalting an asphaltic base crude oil which is non-pumpable at ambient temperatures which comprises the steps of (1) emulsifying water, a crude oil selected from the ,group consisting essentially of Monagas Zone II crude oil from Venezuela, Hamilton Dome crude oil of Wyoming, Oregon Basin crude oil of Wyoming, and Kern River." crude oil of California, and a nonionic emulsifying agent having the general formula:

where R. is selected from the group consisting of hydrogen, aryl and alkaryl radicals; and x, y and z are integers, such that (a) when x is zero, y is also zero, z is in the range of 20 to 60, inclusive, and R is one of said aryl and alkaryl radicals, and (b) when x and y are jgreater' than zero, the sum of x and z is in the range of 50 to 350, inclusive, and y is in the range of 40 to 60, inclusive at a rst point to form an oil-in-water emulsion; (2) pumping said emulsion through a pipeline to a second point; {3} physically breaking the emulsion by centrifuging into an. oii phase and an aqueous phase; (4) separating said aqueous phase from said oil phase; (5) pumping a portion of said aqueous phase containing said emulsifying agent to said first point for reuse in step l; and (6) introducing a portion of said aqueous phase containing said emulsifying agent into the oil bearing formation of said crude oil to aid in recovery of the crude oil which is utiiized in step 1,

10, A process according to claim 9 wherein the crude oil is Monagas Zone II crude oil and said emulsifying agent is a polyoxyethylated alkylphenol having the formula.:

l@ wherein n is an integer from 25-35, inclusive, and aver ageslv@n References Cited UNITED STATES PATENTS 2,533,878 12/1950 Clark et al. 137-436Y 2,981,683 4/ 1961 Simpson et al. 252--8.3 3,006,354 1.0/1961 Sommer et al 137-13 3,107,726 10/1963v Greenwald 166--8 3,108,059 10/ 1963 Greenwald 208-11 FOREIGN PATENTS 561,353 8./1958 Canada.,

STEPHEN I, NOVOSAD, Primary Examiner

Images