Research And Application Of The Lamadian Oilfield Inefficient And Ineffective Circling Loop Identification Methods

The Lamadian oilfield is a nonmarine sandstone oilfield, which is nonhomogeneous due to river facies sedimentary formation of the reservoir. It has been waterflooded for 30 years and has been in particular-higher containing water development period since 1997. During this period, petrophysical parameters of the reservoir, pore structure, fluid distribute etc. have been through a series of varieties which can be reflected in the logging curve. Core analysis of examining well, indoors substance module experiment and field dynamic monitoring material show that there exist serious inefficacy and low efficacy in inhomogeneous multilayer sandstone oil field made of mainly thick layer when the comprehensive saturation is up to 90%. Abundant injected water circulates ineffectively or low effectively through convenient channel with high permeability and high saturation (which is called bighole in abbreviation).The existence of bighole results in low recovery ratio, production cost rising and development benefit descending, which bring substantial pressure to the oil field development. Coupled with conventional open hole logging curves, the research on bighole is useful for tertiary recovery, blocking profile adjusting and injection structure adjusting, and improving the volume of reservoir sweep and reservoir recovery.It is divided into two segments, thin layer and thick layer. The two research blocks are as following: test area of identifying and administering the bighole in the northeast of Lamadian oilfield, there are 212 oil/water wells in all, of which 56 infill wells and 41 polymer flooding wells as data (thick layer); gas/oil buffer zone in the north-north of Lamadian oilfield, there are 135 oil/water wells in all (thin layer), of which 56 infill wells, polymer flooding wells, polymer returning fluid wells as data. The research subjects of identifying and administering the bighole are 5 reservoir groups and 27 sedimentation units. The researches are as following:1. The blocks were researched in fine reservoir geology, exploitation course and production performance, 54 fine reservoir geology maps were made. 85 wells were researched in isotope sop profile, 25 in confinement five combination logging, and more than 120 reservoir connection maps were made.2. Collecting core well data of 5 wells since 2000 all over the oilfield, counting petrophysical parameters of the reservoir and extracting the value of each relative curve, establishing complete database to analyze the relationship between lithologic character and electric property, finding out a curve to distinguish the inefficient and ineffective circling loop and the water flooded zone based on the formation mechanism of inefficient and ineffective circling loop and the microcosmic changes reflected in the logging curve and reservoir parameters, and setting up a criterion to identify the inefficient and ineffective circling loop.3. Establishing ways to identify the inefficient and ineffective circling loop, rebuilding a model to explain the 18 static and dynamic parameters such as reservoir shale content, active porosity, total porosity, bound water saturation, oil saturation, permeability, median grain diameter, pore body radius, water productivity etc. and making up a interpretation program. This research has realized computerization and when it is compared with the core well data, the calculation accuracy can completely meet the demand which is required to identify inefficient and ineffective circling loop.4. Interpreting 212 wells of the test area of identifying and administering the bighole in the northeast of Lamadian oilfield, drawing inefficient and ineffective circling loop in fine geology map and analyzing plane pattern. About 300 inefficient and ineffective circling loop's plane maps of 6 blocks were drawn during three-year period of recognizing, administering, and application. As normal producing project the research is interpreted together with water flooded layer at present.5. Combining with inefficient and ineffective circling loop's vertical data recognition and plane maps and measures such as water shutoff, long rubber barrel's formation sealing, subdivision of reservoir's infusion, perforations, repeat gun perforation etc., many kinds of treatment methods, working processes and management system about inefficient and ineffective circling loop's administering were summed up. It has realized the effective administration of inefficient and ineffective circling loops in three blocks. It also becomes basic foundation for tapping the remaining oil in thick layer, compiling development plan, and analyzing production performance etc., and provides support for further and comprehensive development of oilfield.