Abstract
Abstract
Daqing Oil Field started industrial scale polymer (polyacrylamide) flooding in 1996. More than 3,000 wells are on polymer flood. The cumulative production by polymer flood is more than 400 million bbl, and annual production of year 2002 about 80 million bbl.
Actual field economic data show that the total cost (including depreciation) per bbl of polymer oil is about $9, the same as water flooding in the same area. Analysis of the data show that high incremental recovery (about 12% OOIP - original oil in place), high production rate (about 4 times that of water flooding) and low water oil ratio (a decrease of about 5 fold) are the main reasons polymer flooding obtained such good economic results.
Introduction
Polymer flooding has been field tested for more than 30 years and Daqing Oil Field has industrial scale implemented it for 7 years. In this period, many papers have been written on the technical aspects of the field tests. However, little has been written about the economic results of polymer flooding. Therefore, one question is often asked: "Is polymer flooding economical or not?"
This paper introduces the actual field economic data of industrial scale polymer flooding in Daqing. The data are analyzed and conditions that can cause the production cost of polymer flooding to be lower than (or about the same as) water flooding are pointed out.
Field Results
The field results of 6 industrial scale polymer flood areas [1] are shown in Figure 1. These areas are of 59.11 km2 and have a total of 1,012 wells. Before polymer flooding, the water cut by water flooding was about 90% to 95%. Usually 0.57 PV of a concentration of 1,000 mg/L polyacrylamide with a molecular weight of 12 to 15 million Daltons is injected, followed by water flood till the water cut reaches 98%.
It can be seen that the incremental recovery is about 12% OOIP (original oil in place) higher than water flooding (when both reach a water cut of 98%), the water cut decreases from 90% ~ 95% to about 70% (water oil ratio decreases from 12 ~ 20 to about 2.3, a 5 ~ 8 fold decrease). The production rate for polymer flood is about 4 times higher than that of water flooding (increased from about 40 bbl/d to about 160 to 180 bbl/d). The total amount of fluid injected after initiating the polymer flood until the water cut reaches 98% is about 1 PV, while for water flooding it would be an average of 2.6 PV, therefore much less fluid is injected, produced and treated.
Field Economic Data
The actual field economic data of polymer flooding and water flooding of adjacent areas is shown below.
The costs are subdivided into the following 18 categories:Material cost of all wells, metering station, gathering station and pipelines during production.Fuel cost, cost of all solid, liquid and gaseous state fuels used during production.Power cost, mainly cost of electric power.Salary cost of all employees at production teams and gathering station, including all pay, bonuses and subsidies.Employee welfare cost, this is taken as 14% of the total salary cost.Flooding material cost, mainly cost of injected water and polymer.Down-hole service cost, including the cost of fracturing, acidizing, re-perforating, water shut-of, and down-hole remedial work.Maintenance cost, including the cost of maintaining all major and auxiliary production equipment.Well testing cost.Cost of reclaiming liquefied petroleum gas.Produced liquid (oil, water and gas) treatment cost, including cost of oil-water separation, gas separation and treatment of waste -water.Transportation cost, including cost of transportation and the relevant maintenance fees for roads and rivers (canals).Other direct production costs not included in the above categories.Team management cost.