Lignosulfonate-formaldehyde condensation products as additives in oil recovery processes involving chemical recovery agents

A process for producing petroleum from subterranean formations is disclosed wherein production from the formation is obtained by driving a fluid from an injection well to a production well. The process involves injecting via the injection well into the formation an aqueous solution of lignosulfonate-formaldehyde condensation products as a sacrificial agent to inhibit the deposition of surfactant and/or polymer on the reservoir matrix. The process may best be carried out by injecting the lignosulfonate-formaldehyde condensation products into the formation through the injection well mixed with either a polymer, a surfactant solution and/or a micellar dispersion. This mixture would then be followed by a drive fluid such as water to push the chemicals to the production well.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the recovery of oil from subterranean formations 
by chemical flooding methods. 
2. Description of the Prior Art 
Petroleum is frequently recovered from subterranean formations or 
reservoirs by permitting the natural energy of the reservoir to push the 
petroleum up through wells to the surface of the earth. These processes 
are referred to as primary recovery methods since they use the natural 
energy of the reservoir. However, a large amount of oil, generally in the 
range of 65-90% or more, is left in the subterranean formation at the 
conclusion of the primary recovery program. When the natural reservoir 
energy is unable to produce more petroleum, it is a common practice to 
resort to some form of supplemental recovery technique in order to recover 
additional petroleum left in the subterranean formation. These 
supplemental operations are normally referred to as secondary recovery 
operations. If this supplemental recovery operation is the second in a 
series of such operations, it will be referred to as a tertiary recovery 
operation. However, the terminology is unimportant for the purposes of 
this application and relates only to the sequence in which they are 
carried out. 
The most widely used supplemental recovery technique because of its ease of 
implementation and low capital outlay is water flooding through injection 
wells drilled into the subterranean formation. In a water flooding 
operation, the injected fluid displaces oil through the formation to be 
produced from the injection well. A major disadvantage to water flooding, 
however, is its relatively poor displacement efficiency largely due to the 
fact that water and oil are immiscible at reservoir conditions and high 
interfacial tension exists between the flood water and the oil. For this 
reason, after a water flood, a large portion of the oil is still left 
unrecovered in the reservoir. 
It has been recognized by those skilled in the art that a solution 
effecting a reduction in this interfacial tension between water and oil 
would provide a much more efficient recovery mechanism. Therefore, the 
inclusion of a surface active agent or surfactant in the flood water was 
recognized as an acceptable technique for promoting displacement 
efficiency of the reservoir oil by the water. For example, U.S. Pat. No. 
3,468,377 discloses the use of petroleum sulfonates in water flooding 
operations and U.S. Pat. No. 3,553,130 discloses the use of ethylene oxide 
adducts of alkyl phenols for the same purpose. The use in water flooding 
operations of water soluble surface active alkaline earth resistant 
polyglycol ethers is disclosed in U.S. Pat. No. 2,233,381. Other 
specialized surfactants, as will be discussed later, have been discovered 
to have special properties useful in water flooding operations such as a 
tolerance for high salinity and calcium, and/or magnesium ion 
concentrations often found in reservoir waters. 
However, field operations employing surfactants and surface active agents 
in injected fluid have not always been entirely satisfactory due to the 
fact that these materials are often adsorbed by the formation rock to a 
relatively high degree, resulting in an ever declining concentration of 
the materials as they progress through the reservoir. Therefore, large 
concentrations of surface active materials have heretofore been necessary 
to maintain a sufficient concentration at the oil-water interface. Due to 
this, many proposed flooding operations involving surface active materials 
have been uneconomical. 
Another serious problem for any recovery technique involving the driving of 
oil with a fluid is premature breakthrough of the injection fluid. This 
premature breakthrough indicates that the reservoir has not been 
adequately swept of oil. The problem is often described in terms of sweep 
efficiency as distinguished from the displacement efficiency described 
above. Displacement efficiency involves a microscopic pore by pore 
efficiency by which water displaces oil, whereas sweep efficiency is 
related to the portion of the reservoir which is swept and unswept by the 
injected fluid. A major cause of poor sweep efficiency is associated with 
the fact that the injected fluid generally has a lower viscosity than the 
displaced fluid (petroleum). Thus, the injected fluid has a higher 
mobility and tends to finger through the oil, prematurely breaking through 
to the production well. 
One solution to this high mobility problem is to increase the viscosity of 
the driving fluid. A way to do this is to add polymeric organic materials 
to a driving water which has the effect of increasing the viscosity of the 
water, thereby increasing the sweep efficiency of the supplemental 
recovery process. U.S. Pat. No. 3,039,529 and U.S. Pat. No. 3,282,337 
teach the use of aqueous polyacrylamide solutions to increase the 
viscosity of the injected fluid thereby promoting increase sweep 
efficiency. Polysaccharides as taught in U.S. Pat. No. 3,581,824 have been 
used for the same purpose. These polymers are quite expensive and any 
polymer lost to adsorption on the reservoir matrix adds substantially to 
the cost since additional polymer is required to maintain a given 
viscosity. 
The above described problems have been recognized by those skilled in the 
art of oil recovery and certain sacrificial compounds have been added to 
pretreat the formation in order to decrease the adsorption of subsequently 
injected surfactants and/or polymers. For example, U.S. Pat. No. 3,424,054 
discloses the use of aqueous solutions of pyridine; U.S. Pat. No. 
3,469,630 discloses the use of sodium carbonate and inorganic 
polyphosphates, and U.S. Pat. No. 3,437,141 discloses the use of soluble 
carbonates, inorganic polyphosphates and sodium borate in combination with 
saline solution of a surfactant having both a high and a low molecular 
weight component. These materials have not been completely satisfactory 
from a standpoint of performance and economics however. 
SUMMARY OF THE INVENTION 
The invention is a process of producing petroleum from subterranean 
formation having an injection well and a production well in communication 
therewith. The process comprises injecting into the formation via the 
injection well an aqueous solution of lignosulfonate-formaldehyde 
condensation products in conjunction with a chemical oil recovery agent, 
for example, surfactant, polymer and/or a micellar dispersion. It is the 
usual practice to then inject a fluid such as water to sweep the chemical 
components through the reservoir to the production well, thereby 
displacing oil from the subterranean formation to the surface of the earth 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A sacrificial material is injected by the process of this invention through 
an injection means comprising one or more injection wells into a 
subterranean petroleum-containing formation to preferably occupy or cover 
all potential adsorption sites of the rock within the subterranean 
formation thereby reducing the extent of adsorption of the more expensive 
chemical oil recovery agent injected therewith. A sacrificial agent 
performs best when it exhibits high adsorption on active sites of rock 
surfaces, and thus diminishes surfactant and/or polymer adsorption. 
Chemical compounds of polyelectrolytic nature have the proper physico 
chemical and structural requirements to behave as successful sacrificial 
agents. The functional group on the sacrificial agent molecules enhances 
adsorption either by hydrogen bonding or electrostatic attraction to 
active sites on the rock surfaces. 
A satisfactory sacrificial material has at least three important 
characteristics. First, it should be less expensive than the polymer or 
surfactant on a cost effectiveness basis since it is to be sacrificed or 
adsorbed by the formation, probably not to be recovered. Next, it must be 
adsorbed readily by the subterranean formation matrix. Preferably the 
sacrificial material should be adsorbed more readily than the chemical oil 
recovery agent to be used in the process. The third important 
characteristic of a sacrificial agent is that the presence of such 
adsorbed sacrificial material should retard or eliminate adsorption of the 
surfactant and/or polymer chemical recovery material on the adsorption 
sites of the formation rock. By adsorption sites of the formation rock it 
is meant those parts of the surfaces of the pores of the formation rock 
capable of adsorbing a chemical compound from a solution on contact. 
The sacrificial material may not have a detrimental effect on the recovery 
efficiency of the chemical flooding operation. Additional oil is usually 
recovered only if the sacrificial material is followed by or is admixed 
with a surfactant and/or a polymer chemical recovery agent which will 
effectively increase the amount of oil displaced from the subterranean 
formation. In one embodiment of my invention, surfactant is chosen as the 
chemical recovery agent. The surfactant should be injected in admixture 
with the sacrificial agent for best results and ahead of the following 
flooding water thereby achieving the desired interfacial tension reduction 
between the injected fluid and the displaced fluid with minimal loss of 
surfactant on the formation matrix. The surfactant may be present in a 
hydrocarbon solvent or in an aqueous or in a combination thereof. Any 
anionic, nonionic and/or cationic type surfactant effective for recovering 
oil may be used in this invention. 
The amount of surfactant which must be employed in the practice of any 
chemical flood is generally known in the art and is to be found in 
published literature. However, the slug size of surfactant generally will 
range from about 0.01 to 1 pore volumes of an aqueous surfactant solution 
having dissolved therein from about 0.01 to about 10.0 percent by weight 
of the surfactant itself. 
Another embodiment of my invention is the use of 
lignosulfonate-formaldehyde condensation products in conjunction with an 
emulsion of water, hydrocarbon and surfactant, i.e. a micellar dispersion. 
The same parameters as discussed above for simple aqueous surfactant 
solutions would apply to micellar dispersions. Micellar dispersions are 
known in the art. See, for example, U.S. Pat. No. 3,536,136 incorporated 
here by reference. 
In another embodiment of my invention, the sacrificial agent disclosed 
herein is used in conjunction with polymeric materials which lower the 
mobility ratio and increase the sweep efficiency of the displacing fluid. 
For example, U.S. Pat. No. 3,039,529 discloses the use of polyacrylamide 
solutions for this purpose, and U.S. Pat. No. 3,581,824 discloses the use 
of polysaccharides. Other polymeric materials known to those skilled in 
the art are useful as well, and the specific examples above are given only 
for illustration. 
The method of my invention includes the use of lignosulfonate formaldehyde 
condensation products in conjunction with one or a combination of two or 
more types of chemical recovery agents especially those discussed above. 
In my invention the sacrificial agent is preferably injected in admixture 
with the chemical recovery agent(s) into the petroleum formation. This 
chemical recovery agent/sacrificial agent mixture may or may not be 
preceded by a slug of sacrificial material in aqueous solution only. A 
preflush of sacrificial agent followed by chemical recovery agent is also 
included in my invention but may not perform as well as other embodiments 
although it will generally show an improvement over using no sacrificial 
agent. 
In any of these embodiments and others which are obvious to those skilled 
in the art, the chemical recovery agent containing slug may be followed by 
a material to taper the viscosity before drive water is injected. This 
technique known well to those skilled in the art prevents the water from 
fingering into the more viscous chemical recovery agent slug. 
The sacrificial agents useful in the process of my invention are 
lignosulfonate-formaldehyde condensation products. Lignosulfonates are 
anionic polyelectrolytes soluble in water and tolerate hard water 
(polyvalent ions, e.g. calcium and magnesium). They are also thermally 
stable in formations where the temperature is high. Lignosulfonates are 
macro-molecules built up by complex condensation of phenyl propane units. 
The sulfonate groups are attached to the aliphatic side chain, mainly to 
alpha carbon. Lignosulfonates are water soluble with molecular weights 
ranging from several thousand to around 50,000 or more. They are 
economically attractive since being by-products of the pulping industry, 
they are plentiful and cost less than either the surfactants or the 
polymers used in enhanced oil recovery methods. The polyelectrolyte 
lignosulfonates with strongly ionized sulfonate groups are negatively 
charged species and have a tendency to adsorb on solid surfaces thereby 
imparting a negative charge to them. The rock surfaces of a reservoir 
treated with lignosulfonate will be inert towards the anionic surfactants 
in the flood water and therefore loss of surfactants to the rock surfaces 
will be kept to a minimum. The same phenomenon will occur with the polymer 
thickened drive fluid. 
Lignin is second only to cellulose as the principal constituent in wood. 
Generally, lignin is a complex phenolic polyether containing many 
different functional groups including carboxyls, carbonyls, and alcoholic 
and phenolic hydroxyls. Lignins and their derivatives are described in 
Kirt-Othmer Encyclopedia of Chemical Technology, Second Edition, Vol. 12, 
beginning at page 362. This publication describes two very broad classes 
of lignin derivatives: sulfite lignins and alkali lignins. 
The difference in the lignins exists because of the method of extraction of 
lignin material from woody materials. Sulfonated alkali lignins are 
readily available commercially from various sources including but not 
limited to West Virginia Pulp and Paper Company under the trade name REAX. 
Their general method of preparation is described in the Encyclopedia of 
Chemical Technology referred to above. Briefly, sulfonated alkali lignins 
are prepared by cooking woodchips with a 10% solution of a mixture of 
sodium hydroxide with about 20 mole percent of sodium sulfide. The lignin 
with wood is modified into a sodium compound often termed sodium lignate 
or alkali lignin which is very soluble in the strongly alkaline solution. 
These alkali lignins are removed from solution by lowering the pH which 
precipitates out the alkali lignins. These unsulfonated alkali lignins are 
sold under various tradenames including INDULIN. These alkali lignins are 
used to prepare the sulfonated derivatives. Methods of sulfonation are 
known by those skilled in the art. One typical method involves treating 
the alkali lignins with a solution of alkali sulfites at elevated 
temperature and pressure. The degree of sulfonation may be controlled to 
provide a variety of sulfonated alkali lignins. 
The other main type of lignin derivatives are called sulfite lignins or 
sulfite lignosulfonates. Sulfite lignins are generally made by cooking 
woodchips under pressure in a solution of sulfurous acid and calcium, 
magnesium, sodium or ammonium bisulfite. This process converts insoluble 
lignins to soluble lignosulfonic acid. The lignosulfonic acids or calcium, 
magnesium, sodium or ammonium salts of the lignosulfonic acids are 
available under various tradenames including MARASPERSE, LIGNOSITE, ORZAN, 
TORANIL, and RAYFLO. 
The broad term lignosulfonates used herein refers to both sulfonated alkali 
lignins and sulfite lignosulfonates (sulfite lignins). These are distinct 
types of compounds as explained above. Since the alkali lignins require 
sulfonation after extraction of the material from woody products it is 
proper to call them sulfonated alkali lignins. Likewise since sulfite 
lignins emerge from the extraction process already sulfonated it is proper 
to refer to this class of materials as sulfite lignins or sulfite 
lignosulfonates. 
My invention is the use of formaldehyde condensation products of sulfonated 
alkali lignins and/or sulfite lignosulfonates. Lignosulfonates having 
degrees of sulfonation from about 2.0 to saturation are acceptable as 
starting materials for the lignosulfonate-formaldehyde condensation 
products of my invention. Cations which are acceptable include Na.sup.+, 
K.sup.+, NH.sub.4.sup.+, CA.sup.++, and Mg.sup.++. The degree of 
sulfonation is the weight percentage of sulfonate (SO.sub.3.sup.-) 
compared to the total molecular weight. 
Lignosulfonates polymerized with formaldehyde will have the needed 
molecular size to exhibit high adsorption on rock surfaces, and therefore 
perform as better sacrificial agents in surfactant systems. 
Lignosulfonate-formaldehyde condensation products may be improved by either 
using modified lignosulfonates as the starting compound and then 
condensing with formaldehyde or by modifying the 
lignosulfonate-formaldehyde condensation products. The salt and hard water 
tolerance of lignosulfonate-formaldehyde condensation products can be 
improved by sulfomethylating the lignosulfonate-formaldehyde condensation 
products. On the other hand, higher molecular size lignosulfonates may be 
obtained by first oxidizing the lignosulfonate (See U.S. Pat. No. 
4,133,385) and then condensing it with formaldehyde. Carboxylated 
lignosulfonates (See application Ser. Nos. 900,691 and 900,692, now U.S. 
Pat. No. 4,172,497, filed Apr. 27, 1978) may also be used as the compound 
prior to condensation in order to obtain carboxylated 
lignosulfonate-formaldehyde condensation products as a final product. 
Both sulfite lignosulfonates and sulfonated Kraft lignin can be utilized in 
the formaldehyde condensation reaction. The formaldehyde condensation 
reaction can either be alkali-catalyzed or acid-catalyzed. The 
alkali-catalyzed reaction does not yield a high molecular weight product 
and, therefore, the acid-catalyzed condensation is the preferred reaction. 
In the acid catalyzed reaction formaldehyde attaches on the ortho position 
to the propyl group. Condensation of lignosulfonates with formaldehyde may 
be carried out, for example, by refluxing a lignosulfonate solution (about 
6% w/w) for 24 hours or more with an aqueous formaldehyde solution (37%) 
and concentrated sulfuric acid. The reaction can be terminated at any time 
when the viscosity of the products reaches a preferred value. 
Lignosulfonate-formaldehyde reaction products obtained by terminating the 
reaction (methylolation) before intermolecular condensation occurs can 
also be used for the same purposes. Methylol groups can thus be introduced 
to the lignosulfonate structure, and enhance the effectiveness of the 
modified lignosulfonate as a sacrificial agent. 
Norlig 92 g (softwood and desugared lignosulfonate) was condensed with 
formaldehyde as above and the product (supplied by American Can Co.) was 
tested as sacrificial agent with 1%, w/v Adduct D-30 PS* in 40,000 ppm TDS 
brine. Bottle tests were performed with 1%, w/v lignosulfonate solutions 
at 43.degree. C. using crushed Slaughter core material as the adsorbent. 
The surfactant adsorption values are given below: 
FNT *Propane sulfonate derivative of the three (3) mole ethylene oxide adduct 
of dodecyl phenol. 
______________________________________ 
Lignosulfonate Surfactant Adsorbed 
1%, w/v mg/g 
______________________________________ 
None 4.9 
Norlig 92g-Formaldehyde 
Condensation Product 
1.7 
______________________________________ 
Results indicate that the lignosulfonate-formaldehyde condensation product 
decreased surfactant adsorption from 4.9 to 1.7 mg/g of rock, and that it 
should perform as an effective sacrificial agent when utilized in 
surfactant flooding processes. 
Crude unmodified lignosulfonates may be made with either softwoods or 
hardwoods. Although having basically the same functional groups the crude 
unmodified softwood lignosulfonates have more sulfonate and hydroxyl 
groups than the crude unmodified hardwood lignosulfonates. Thus, in 
general, crude unmodified softwood lignosulfonates have better hard water 
(Ca.sup.++), Mg.sup.++) tolerance than the hardwood form. 
The quantity of lignosulfonate-formaldehyde condensation product to be 
injected into the subterranean hydrocarbon formation may be any amount up 
to and including an amount sufficient to occupy substantially all of the 
active sites of the formation matrix. If less than the maximum amount is 
used, there will be a corresponding increase in the adsorption of 
surfactant form injection solution onto the formation matrix although the 
amount of increase will not be as great as in the case where the formation 
is completely free of lignosulfonate salts. At a maximum, only the amount 
of lignosulfonate-formaldehyde condensation products needed to completely 
occupy the active sites on the formation matrix is needed. The detriment 
resulting from using excess lignosulfonate-formaldehyde condensation 
products would be an increase in the cost of operating the oil recovery 
program. 
The amount of lignosulfonate-formaldehyde condensation products salts 
needed in the process of the invention depends on the particular 
formation, the area or pattern to be swept and other formation 
characteristics. Those skilled in the art can determine the exact quantity 
needed to afford the desired amount of protection. 
Generally it has been found that the amount of lignosulfonate-formaldehyde 
condensation products in the surfactant slug will be effective in amounts 
of from about 0.01 to about 10.0 percent by weight of the total surfactant 
solution (including the aqueous portion). Total 
lignosulfonate-formaldehyde condensation products will be effective at the 
above concentrations in amounts ranging from 0.01 to 1.0 pore volumes of 
the aqueous solution of surfactant-sacrificial agent or only sacrificial 
agent solution. 
ILLUSTRATIVE FIELD PROCEDURE 
A carbonate reservoir at a depth of 5,000 feet with a porosity of 15% and a 
permeability of 50 md is water flooded to a residual oil saturation of 
36%. In order to recover additional oil from the reservoir, a chemical 
flood comprising an aqueous 2.5% solution of lignosulfonate-formaldehyde 
condensate as described above and a 2.5% surfactant solution comprising 
0.55% petroleum sulfonate of 497 equivalent weight, 1.2% petroleum 
sulfonate of 332 equivalent weight, and 0.75% of sulfonated 6.0 mole 
ethylene oxide adduct of nonyl phenol is pumped into the reservoir through 
an injection well in an amount comprising 0.3 pore volume of the 
reservoir. This slug of sacrificial agent surfactant solution is followed 
by an aqueous solution of 0.1% polysaccharide in a slug comprising 0.6 
pore volume. The polysaccharide solution is followed by water and the 
entire chemical system is displaced to five (5) production wells 
surrounding the injection well. At the end of the chemical flood, the 
reservoir has an oil saturation of 16% representing a recovery of 56% 
additional oil.