An investigation of the use of surface-active agents in the secondary recovery of oil by water flooding

The importance of producing oil cannot be emphasized enough in this modem world. Therefore, when primary methods of production seemingly exhaust the oil reservoirs, a secondary method of producing more oil is a necessity. At the present time, secondary methods of oil recovery have developed into a large industry. They are not a new development. The need of introducing compressed air or air-gas mixtures into the wells to increase production was quickly realized. Water flooding methods followed, and at first were restricted to the Eastern fields. Later, about 1935, systematic water flooding methods were developed and applied all over the country. The system of water flooding involves applying water under pressure to oil-bearing formations by means or injection wells, generally ringed around a production well. These formations are fine-grained, tightly-packed sands, which contain oil left in the formation after the primary method of\u27 production. The mechanics of the flooding involves the formation of an oil bank ahead of the advancing water and its removal through the production well. Water flooding at the present time is a very inefficient process, due to the fact that approximately 25 per cent of the oil is left in the formation after the flood. If this oil, or even a part of it, could be removed by a special kind of water drive it would greatly increase the income of the operator but also would reduce the amount of oil left in the formation which now is unobtainable by any present methods of production. The use of wetting agents or surface-active chemicals has been prominent among the methods which have been proposed to reduce the amount of residual oil by water flooding. It is theoretically possible to sweep more oil out of the sand by using surface-active chemicals to lower the surface tension of the water and the interfacial tension between the oil and water. This fact has been known for some time. The principal feature cited in argument against the use of wetting agents has been excessive adsorption onto the reservoir rock surface. The advancing water front of the flood, therefore, has been depleted of these agents before beneficial effects could be realized. The amount and cost of the chemicals required to permit an effective penetration of the reservoir has been entirely out of proportion to the value of the additional oil that might be obtained. However, almost all of the early experiments were conducted using cationic and anionic wetting agents. During the past few years non-ionic surface-active agents have become available at a low enough price to make their use in water flooding a practical matter. In laboratory tests these chemicals have shown a negligible tendency to become adsorbed by siliceous or clay minerals. From these results, it seems that the problem of excessive adsorption has been solved by the use of non-ionic wetting agents. Most investigators of this subject have agreed that not all reservoirs respond in the same manner to the same chemical. The reasons why a certain surface-active agent is very effective on one type of reservoir formation and only moderately so or not at all on a different reservoir formation are not known completely at the present time. Therefore, to establish the effectiveness of a certain surface-active chemical upon a particular reservoir, laboratory flooding tests as well as a pilot flood test should be carried out. The subject matter of this thesis is the experimental investigation of the effects which certain surface-active chemicals have upon the residual oil content after water flooding or cores taken from Shell-Saunders No. 1 Well, located in the Canary Field, Washington County, Oklahoma. All surface-active agents tested were of the nonionic water-soluble type. To the author\u27s knowledge, no such investigation has been made using these surface-active chemicals, nor have cores from this field been tested in this manner --Introduction, pages 1-3