Study on Technical Measures of Romashkino Oil Field after Entering Ultra-High Water Cut Stage

doi:10.4236/eng.2013.57074

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Engineering, 2013, 5, 622-628

http://dx.doi.org/10.4236/eng.2013.57074 Published Online July 2013 (http://www.scirp.org/journal/eng)

Study on Technical Measures of Romashkino Oil Field

after En t er ing Ultra-High Water Cut Sta ge

Liuli Lu1,2, Zhibin Liu1, Haohan Liu1,3*, Yongqin Yan1

1School of Graduate of Southwest Petroleum University, Chengdu, China

2Geological Exploration and Development Institute of Chuanqing Drilling Engineering Co., Ltd., Chengdu, China

3Sichuan College of Architectural Technology, Deyang, China

Email: *[email protected]

Received May 6, 2012; revised June 6, 2013; accepted June 14, 2013

permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Romashkino oil field has large oilfield area, small formation dip, many reservoir layers, wide oil-water transition zone

and complicated sedimentary environment. Since development, 3 overall development plannings and adjustments of

individual block have been established. This achieves a high oil production. However, the recoverable reserves of major

oil layer with high production become smaller and smaller and the water cut increases over time, the production ability

of oil layer decreases. The development status of oil layer of mining siltstone, oil-water transition zone and oil layer

with upswept injected water cannot be changed under present dilute well network condition, because there is no rein-

forced measurement to water well. This results the low oil production of Romashkino oil field. In order to improve oil

production rate and reach the designed oil recovery, Romashkino oil field has been implemented many added cuttings

since development. Resent researches about Romashkino oil field show: in later oilfield development stage, sidetrack

and lateral drilling horizontal wells technology is very reasonable; formation hydraulic fracturing technology has been

widely used in recent years; in tertiary oil recovery, sweep efficiency and flooding efficiency related technologies have

been taken. This offers reference and guidance for the effective and reasonable oil field development in later period.

Keywords: Romashkino Oil Field; Geological; Development; Technical Measures

1. Introduction

Romashkino oil field lies in Tatarsta. It was found in

1948, and began industrial development in 1952. In 1954,

Romashkino oil field began to inject water and it was a

typical multi-layer oil field [1,2]. The oily area of Ro-

mashkino oil field is 4255 km2, geological reserves is 45

× 108 m3, the recoverable reserves is 24 × 1088 m3, and

the oil recovery is 53% [3,4]. At present, this oilfield is

in the production decline stage. In 1997, the crude oil

production of Romashkino oil field is 1500 × 104 m3, the

water cut is 0.88, the cumulative oil production is 20.3 ×

108 m3, the recovery degree is 45.1% [5,6]. The location

map is shown in Figure 1.

2. Romashkino Oil Field Geology and

Development

2.1. Tectonic

The area of Romashkino oil field is large and the forma-

tion dip is small, the tectonic area is 4500 km2, where the

oil-water transition zone area is 70% of the total area, the

formation dip is smaller than 0.5˚, and only reaches 2˚ in

the side of south and west. The oil-bearing area of Devo-

nian D-I layer is 4255 km2, tectonic high-point located in

Figure 1. Location map of Romashkino oil field.

*Corresponding author.

L. L. LU ET AL. 623

1535 m below the sea leve [7-9] (see Figures 2 and 3)

(North: 1480 - 1482 m, South: 1489 - 1490 m).

2.2. Sedimentary Facies

The oilfield stratigraphic section is composed of the Pre-

cambrian, Devonian, Carboniferous and Permian strata,

the total sediment thickness is 2000 meters, in which car-

bonate sediment thickness is about 1500 m, the thickness

of the terrigenous is about 500 meters, where 89% of the

proved reserves located in the Paxi Ya group DI sand

layer and Ke Nuofu group D-0 sand layer of the Upper

Devonian. The depositional environment of the sand-

stone reservoir is mainly the delta plain distributary

channel, The lithology consists of quartz sandstone, silt-

stone, mudstone and limestone.

Figure 2. Formation top structure of Romashkino oil fiel d.

Figure 3. Cross-sectional view of D-I oil layer of Romashkino oil field.

L. L. LU ET AL.

624

2.3. Reservoir Properties

il field are 421. 22 oil lay-

major parame-

mperature: 37.8˚C;

9% in aver-

3.1t Design

ashkino oil field has

erty

cutting distance, reinforced the development of oil layer

The proven reservoirs of the o

ers are established. The main oil production layer is D-I

layer, the burial depth ranges from 1650 m to 1850 m.

the oil layer temperature is 37.8 Degrees Celsius, the

original formation pressure is 16.3 - 18.2 MPa, and the

OOIP is 45 × 108 t, other parameters are shown in Tables

1 and 2.

Fluid propertis

The following shown parameters are the

ters of the fluid properties of the production layer of

Romashkino oil field.

Original formation pressure: 16.3 - 18.2 MPa;

Saturation pressure: 8.5 - 9.5 MPa;

Original gas-oil ratio: 40 - 65 m/t;

Oil density: 0.858 g/cm;

Viscosity: 2.6 - 4.5 mPa·s;

Wax content: 3.2%;

Sulfur content: 1.3%;

The original reservoir te

The original water saturation: 17% - 21%, 1

In a word, the major characteristics of Romashkino oil

field are the followings: large area; big the formation dip;

many oil layers; wide oil-water transition zone and com-

plicated sedimentary environment.

3. Romashkino Oil Field Development

Characteristics

. Oil Developmen

Since development in 1952, Rom

been made three total development program [11,12].

1) The first total development program (in 1956)

pAccording to the geological structure, reserve pro

d oil-water interface factors, Romashkino oil field is

cutting into 21 development zone with water injection

wells, the yearly oil production is 5400 × 104 ton. The

injection and production of D-I layer is reasonable, the

bottom-hole pressure of production well is 12.5 MPa, the

wellhead pressure of injection well is 6 MPa, water line

pressure is17.5 MPa (see Figure 4).

2) The second total development program (in 1966)

The second total development program declined t

with low and middle permeability. The main idea of this

program is to keep stable production after entering high

oil production; move the water line in completely flooded

area, reservoir with good connectivity and homogeneous

region; increase 50 percent oil production. The designed

oil recovery of each cutting section is 40% to 55%. In

order to solve the hierarchical differences, the develop-

ment program formulates to take separate water injection

and oil production.

3) The third total development program (in 1976 to

Figure 4. Depositional environment of DI-D0 oil layer.

D-I layerPorosity

Table 1. Data of BXY group D-I layer.

Thickness of production permeability

layer (m) (mD) (%)

a 1.8 - 7.1 1 1 57 - 5894 - 23

b1 2.8 541 22

b2 2.2 317 19

b3 2.9 411 22

v 1.2 141 14

2153 12

9 - 3.2 - 733 - 2

g1 2.9 300 - 400 20

g2-3 6.6 824 21

d - 3.7 6 - 554 - 2

f main reservoir.

project D-I D-I D-0

Table 2. Data o

D-0 project

Total thickness of 20 - 50 20 - 40 permmD 142 - 824, average 375 100 - 800, average 300

reservoir/m eability/

Effective thickness o

3.7 - 16.9 <4, aver2

Net-gross ratio Initon

reservoir/m 6, average 8.age 3.porosity/% 13 - 24, average 19 10 - 22, average 18

0.56 - ial oilsaturati17 - 21, average 19 -

L. L. LU ET AL. 625

The water injection system is further reinforced, the

ed area is enlarged, the additional wells are

ent zones in the later develop-

minly ad-

nuous oil layer with low oil production reservoir

n in the A oil layer of Ali-

development

pment zone and carry out side water injection and

of Qishiming development zone; en-

ter i

opment Stages

ield

into four stages, they are:

aracteristics of Oil Field Development

characteristic curve is a line, water cut of

177)

water flood

pt drilled, the wells network is encrypted and the pro-

duction decline rate is controlled to reach the designed

oil recovery. To reinforce water injection system needs

the ratio of injection well and production well to be 1:3;

for the independent well network with connectivity layer,

the upper reservoir injection pressure should be higher

than the lower reservoir; selective injection in the oil

water transition band.

4) Key adjustment in five development Zones

In 1986, five developm

ent period of Romashkino oil field were ma

sted.

1) Establish separate point-like injection system in the

disconti

Rakhmanov block; carry out supplementary cutting in

the high production oil layer and establish separate mas-

sive water injection system;

2) Establish supplementary cutting wells aims to de-

velop periodic water injectio

fu and Dongsuyefu development zone;

3) Establish stratified water injection system and sup-

plementary cutting wells in the Qishiming

ne;

4) Use the 600 × 600 m well network in the Saernuofu

develo

rizontal cutting;

5) In addition, carry out phased drilling in the low

permeability layer

ypt well spacing density to 300 × 600 m in the later

period of Saernuofu development zone; do not drill well

in the area with siltstone thickness less than 2 m and

without wanjection system.

3.2. Division of Oilfield Devel

After introducing statistics to the Romashkino oil f

gives Figures 5 and 6.

From Figures 5 and 6, we divide the Romashkino oil-

field development stage

1) the first stage (1952-1969): incensing oil production

stage;

2) the second stage (1970-1975): stable oil production

stage;

3) the third stage (1976-1992): oil production decline

stage;

4) the fourth stage (since1993): decline slowed down

stage.

3.3. Ch

Characteristics of oil field development are shown

Figures 7-9.

Figure 7 shows: in the second stage of development,

the water cut

lfield increases steadily. With the implementation of

various adjustment measures of the oilfield, a downward

trend of the line slope takes on; Figure 8 shows the sec-

ond characteristic curve can be divided into three line

section: the first line section means the completely de-

velopment of oilfield blocks, water cut increases steadily;

the second line section means the water cut increase

faster and faster, because of the imperfect injection and

production systems; in the third line section, the water

cut keeps 0.87 with the implementation of different mea-

sures.

Figure 5. Yearly oil production and water cut of Romashkino oil field.

L. L. LU ET AL.

626

0.00

5.00

10.00

15.00

20.00

25.00

1952 19561960 1964 19681972 1976 1980 19841988 1992 1996

t/year

Np/10

Figure 6. Cumulative oil production of Romashkino oil field.

100

1000

10000

100000

1000000

051015 20 25

Np/10

Wp/10

Figure 7. First-type water drive curve.

0.001

0.01

0.1

0510 152025

Np/10

WOR/m

Figure 8. Second-type water drive curve.

L. L. LU ET AL.

627

100

0510 1520 25 3035 4045 50

R/%

Figure 9. Relation curve between recovery degree and water cut.

4. Technical Measures of Romas h kino

Oilfield after Entering Ultra-

Cut Stage

4.1. Oilfield Development Problems

1952, Romashkino oil field started to develop, and the oil

production increased by time. In 1970, the oil production

reached maximum—81.50 million tons. From 1976 to

1979, the oil production declined from 77.75 million tons

to 68 million toms, the yearly declining rate is 2.8% -

5.9% [10-12].

4.2. Improvement of Major Technical Measures

of Oilfield Development

1) Improve development system and enhance oil re-

covery

In order to enhance oil p

esigned oil recovery, the R

to 59.

idering the het-

g and mo-

ea step by step. Since 1952, 1 - 2 new

to 37 wells increased to

entary well and encrypt the original well pattern.

The water cut of Romashkino oilfield increase slowly,

duction and water production is low.

This is related to the oil velocity and many measurements

and adjustments.

1) Close the water well with high water cut;

2) Block high water cut layer;

3) Drill additional wells in low water cut area and im-

prove oil production of oil well with little water;

4) Change the fluid flow direction by periodic water

injection and adjust the water injection profile of water

injection well.

Researches in recent years show: in later oilfield de-

velopment stage, sidetrack and lateral drilling horizontal

wells technology is very reasonable; formation hydraulic

fracturing technology has been widely used in recent

years; in tertiary oil recovery, seep efficiency and

flooding efficiency related technologies have been taken.

iant Oil Gas

Recovery (A Case of the Heterogeneous Strata of the

High Water and the fluid pro

roduction rate and reach the

omashkino oilfield carried d

out many additional cutting measurements, form 23

Because the cutting width is narrow, the oil layer volume

th effective water sweep increases 20%, and the oil

production rate increases relatively. Cons

erogeneity, point-like injection, selective fillin

bile water injection, as well as part of the stratified water

injection of injection well with different pressure can be

carried out.

2) Develop with new wells in new blocks

The development process of Romashkino oilfield be-

gins with middle high production area, and expands the

development ar

development Zone has been put into operation. In the

major development stage, production wells are increased

0 - 600 per year, and the injection

- 100. After 1964, Romashkino oilfield began to drill

supplem

3) Take different measures to reduce water production

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