Page 113 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Gas-wetting Alteration Agent and Gas-wetting CHAPTER 3 97

Table 3.13 Contact Angle Data Sheet of Core P27

Liquid Type Distilled Water( ) Oilfield Sewage( ) Crude Oil( )

Comparing 1.69 1.56 35.76
F06-AA-DA 142.45 134.36 97.84

3.2.1.2.4 Analysis of Core Surface Wettability
The synthesized fluorinated acrylate polymer was dissolved into N,N- DMF
with the concentration of 80 mg/L. The core P27 was immersed in it for
6 hours, and then dried at room temperature. Contact angles of distilled water,
oilfield sewage, and crude oil were measured. The measurement of contact
angle was conducted using JC2000D3 contact angle meter at room temperate,
at 65%B70% humidity and 5 μL droplet volume. For every test sample, at
least three different points were chosen for the measurement and the average
value was taken, while images and digital photos of the contact were captured.
The experimental result is shown in Table 3.13.
It can be seen from Table 3.13 that the contact angle of distilled water on the
surface of untreated core PJ27 is 1.69 degrees. If the core is treated with fluori-
nated acrylate polymer, the contact angle reaches 142.45 degrees. At the same
time, the contact angles of oilfield sewage and crude oil are both increased,
i.e., drops on core surface spread rapidly before treatment. The drops present a
spherical shape on the core surface, and there is a huge increase in contact
angle after treatment. Therefore, polymer treatment realizes the alteration of
core surface from liquid wettability to gas wettability.

3.2.1.2.5 Experimental Study of Spontaneous Core Imbibitions
Cores were dried and immersed in 0.2% sodium chloride or kerosene to mea-
sure the capability of imbibitions and core exhaustion. The experimental pro-
cedure is as follows: the core was hung over the balance, a vessel holding
liquid was placed on the balance, and the lift table was moved below the bal-
ance. While the core makes contact with the liquid surface, the balance equals
zero. At the same time, changes in the balance scale were recorded over time.
The fall in scale reading indicates the quantity of liquid that seeped into the
core. The experiment was continued until the scale reading stopped changing.
The proportion of the liquid quantity that seeped into the core and pore vol-
ume of the core was the liquid saturation of the core, namely reservoir imbibi-
tion recovery. Figs. 3.4 and 3.5 show the experimental result.
From Fig. 3.4, it can be seen that when the core is untreated, water seeps into
the core and spontaneously displaces air in the core, and the imbibition rate is
59%. The imbibition rate of cores treated with polymer F06-AA-DA is reduced
to 38.9%.