Proceedings of the Ninth (1999) International Offshore and Polar Engineering Conference
Brest, France, May 30-June 4, 1999
Copyright © 1999 by The International Society of Offshore and Polar Engineers
ISBN 1-880653-39-7 (Set); ISBN 1-880653-40-0 (Vol. I); ISSN 1098-6189 (Set)
Characteristics Study of Hydrocyclone Used for
Separating Polymer-Flood Produced-Water
Zunce Wang, Lixin Zhao, Feng Li and Jie H e
Daqing Petroleum Institute
Anda, China
Lei Chen
DaRing Petroleum Administration Bureau
Daqing, China
ciency, small land-taking and other merits have attracted many scholars
in the world. The hydrocyclones can be classified into two types, static
and dynamic hydrocyclones, according to its structure, and can be also
classified into de-oil (used for disposing oil-contaminated water, where
clean water is needed) and de-water (used for disposing watercontaminated oil, where pureoil is needed) hydrocyclones, according to
its utilities. Now the oil-cut in the PFPW in Daqing Oilfield is about
1000 to 2000 ppm, the used hydrocyclone should still be de-oil type (Jie
He et al. 1997). But due to the differences between PFPW and the
normal oil-contaminated water, the used hydrocyclone should be different with the normal de-oil type. How to solve this problem? We took
the research of the filed characteristics of PFPW in a de-oil type static
hydrocyclone as the key to solve it. After that, field tests of an improved
static hydrocyclone were taken, and a more effective one, dynamic
hydrocyclone, was also tested, and the separation characteristics of the
dynamic hydrocyclone were also studied.
ABSTRACT
Main oilfields in China, such as Daqing Oilfield, have turned to
the period of enhanced recovery, polymer-flooding is a key technical measure to it. Its studies are very important. Firstly, authors
studied the field characteristics, especially for tangent velocity
field, of polymer solution in a static hydrocyclone, from which an
initial theoretical knowledge was obtained. Then, contrast tests
between the static hydrocyclone and the dynamic one used for
separating polymer-flood produced-water (PFPW) were made.
Some useful conclusions were summarized, one of the important
aspects is that the dynamic hydrocyclone is better than the static
one. It is necessary to study and develop the dynamic hydrocyclone
separation technique furthermore.
KEY WORDS: Hydrocyclone, polymer-flood, static, dynamic
INTRODUCTION
STUDY OF STATIC HYDROCYCLONE
Many oilfields in the east of China have turned to the period of
recovering moderate or high water-cut petroleum. The average watercut of the produced fluid in Daqing Oilfield has reached around 85 per
cent. The practice of recent years has verified that the enhanced recovery method of polymer-flood is a key technical measure to the stable
yields of Daqing Oilfield. But a series of problems are still existing in
the technological process of polymer-flood. One of them is the disposal
of the produced-water, which is related to the recovery cost. The suitable treatment is beneficial to the oilfield recovery and the environmental protection.
The enforcement of the technical measure of polymer-flood changed
the characteristics of the produced-water, one of the principal change is
the raising of its viscosity. At the same time the oil-in-water emulsion
is more stable, the oil-water separation turns to more difficult. If the
normal equipment, such as subsidence and filter plants, were used, the
processing time becomes longer, and the land-taking of the surface
facilities enlarges sharply. In order to separate PFPW more effectively,
the gravity is not enough, another certain force must be used. Based on
this consideration, the hydrocyclone separation method is put forward.
The liquid-liquid hydrocyclone separation method is a new separation technology developed in the beginning of the 1980s. Its high effi-
Indoor Test Rig and Research Method
We used a normal de-oil hydrocyclone to study. All the tests were
taken on the self-made hydrocydone test rig. Its test technological
process diagram and its laser measuring diagram were shown in Fig. 1
and Fig. 2.
On the test rig, the downflow water of the hydrocyclone returns to
water tank, so as to circulate. Pressure gauges, flow rate meter and
valves are installed at the inlet, the downflow and the upflow vents.
The flow rate can be adjusted and the pressure values can be recorded
if necessary.
In order to measure any section of the hydrocyclone, the transparent
plexiglas was selected as the material of the test prototype. Because the
shape of the hydrocydone's outer surface is cylinder, the refraction
angle of the two beams projected from the Laser Doppler Velocimeter
(LDV) could be very large. We installed an optical compensate box to
weaken its effect. It was also made by plexiglas, and filled with water.
Correction was also made.
Tests and Data Analysis
226