Abstract

Aimed for the need of oil displacement in high salinity formations where the normal nonionic and anionic surfactants are inefficient because of salting out or cloud point phenomena[1], A novel structure surfactant(LF) with nonionic and anionic hydrophilic group is put forward and synthesized. The said surfactant is soluble in 30% NaCl brine, and shows good surface activity in brine with 100,000mg/L salinity concluding 5,000mg/L CaCl2. By analysizing the volume fraction-salt concentration phase graph, the salt tolerance property of LF, petroleum sulfonate and their combined system is comparatively studied, LF is excellent, the proportional increment of LF in combined system will improves salt tolerance property of the combined system. In any different brine, water/n-decane Interfacial tension is high if only LF or petroleum sulfonate is used, but Interfacial tension will reach super low if the combined system is appropriately used as long as water salinity is enough high(higher than 20,000mg/L). By adjusting the proportion of LF and petroleum sulfonate in combined system, water/oil Interfacial tension can always reach super low regardless of water salinity, so the system can be particularly used as oil displacement agent in high salinity formations. The paper presents three oil displacement and one chemical tuff and puff formulations consisted of LF and KPS, which were suitable for high salinity formations in Zhongyuan oil field.

The temperatures of four test zone are 86.9°C, 65.0°C, 82.5°C and 82.5°C, the salinities are 88,540 mg/L, 55,028 mg/L, 14,9127mg/L and 195,000 mg/L, the room recovery improvement all exceed 19%.

Now the four field tests get along favorably, verifying good result and indicating bright application prospect.

Introduction

Surfactants are widely used in oil field, and the interest in the use of nonionic and anionic surfactants has increased, For example, polyoxyethylenated alkyl alcohol and petroleum sulfonate(PS), but they cannot be used in high temperature and high salinity formations. Nonionic surfactants and anionic surfactants will salt out because of cloud point phenomena and high salinity respectively. Therefore, a novel structure surfactant (LF) with nonionic and anionic hydrophilic group is put forward, it will not only maintain the advantages of nonionic and anionic surfactant, but also overcome the inefficiency[1–4].

In the work, ether caxhoxylated surfactant, as a nonionic and anionic ampholytic surfactant, was industrially acquired, it revealed that the nonionic group is oxyethylene and the anionic group is carboxyl. The structural formula is as follows:

  • C9H19-C6H4-O- (CH2CH2O)8-CH2COONa

C6H4 refer to arykyl.

Experimental Method

Surface tension is measured by vertical plate method. Interfacial tension is measured by the Texas-500 spinning drop interfacial tensiometer, and the value of water/oil interfacial tension is determined with 0.2% concentration of surfactant.

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