Page 248 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

232 Gas Wettability of Reservoir Rock Surfaces with Porous Media

6.4.2 Design, Preparation, and Evaluation of Oily Cutting
Degreaser
Oil-bearing cuttings and degreasers are surfactants. It is, however, difficult
for a single surfactant to achieve degreasingbyachemical washmethodfor
oil-bearing cutting, which is complex and involves various interfacial
phenomena. When the degreasing mixture contains a gas-wetting alteration
agent, the degradation rate improves. Based on the analysis, the relation-
ship of the surfactant structure and performance are key factors affecting
the degradation rate. Synthesis of this type of oily cutting degreaser is
discussed in this section. The results from experimental analysis show that
the degreaser is highly efficient, has a broader spectrum of action, and is
biodegradable.

6.4.2.1 DESIGN, SYNTHESIS, STRUCTURAL ANALYSIS, AND
PERFORMANCE EVALUATION OF MAJOR SURFACTANTS
In fact, oil-bearing cuttings degreaser contains 7 surfactants (gas-wetting alter-
ation agent, polypropylene base propyl sulfate, anionic surfactant A, anionic
surfactant B, nonionic surfactant C, nonionic surfactant D, and nonionic sur-
factant E). The design, structure, and performance of surfactants are mainly
stated as below. The synthesis part of activator, synthesis of polypropylene
base propyl sulfate, and synthesis of gas-wetting alteration agent have all been
stated specifically in Chapter III, “Gas-wetting alteration agent and gas-wetting
alteration mechanism.”

6.4.2.1.1 Molecular Structure of Major Surfactant
Essential properties of degreaser: emulsifying properties, permeability, and
wettability. Emulsifying properties and wettability have mainly been
considered.

First, high oil-removal efficiency and emulsifying capacity of degreaser are
required. The hydrophilic radical at the end of a hydrophobic chain is
chosen to enhance the emulsifying property. Second, as higher wettability
and permeability of surfactant are required, they are achieved by removing
the oil within oily cuttings and replacing it with a hydrophobic group,
which has branches and can improve the wettability. The hydrophobic
group of C 12 has been chosen here. Third, the alkyl sulfate type of surfac-
tant, which is one of the best surfactants to wet, emulsify, disperse, and
2
clean, 2OSO is chosen as the hydrophilic radical and propylene tetramer
3
is chosen as the hydrophobic group to improve the emulsifying capacity
and wettability.
Therefore, the molecular structure of the degreaser can be preliminarily
determined:
CH 3 CH CH 3 ÞCH 2 Þ CH CH 3 ÞOCH 2 CH CH 3 ÞOSO 3 Na
ð
ð
ð
ð
3