Microbial Prospecting Technology For Oil And Gas In The Western End Of Gangxi Structure Research

After50year’s exploration, most of china’s petroliferous basins have been well exploration, and found a lot of oil and gas fields which are apt to discovery. But, followed with further development, the rest of petroleum resources distributed decentralized, oil/gas reservoirs is small, and most of them are non-structural oil-gas reservoirs. If we use routine method, it’s very difficult and the cost is expensive. So MPOG can forecast non-routine oil/gas reservoirs and deep oil/gas reservoirs, can ascertain petroleum resources distributed in geological structure, and can indicate location of oil drainage. It is very important to improve oil/gas exploration.The aims of MPOG are:①delineate hydrocarbon-oxidizing bacteria anomalies region which is relate with deep oil/gas reservoirs, indicate location, provide an experimental basis for exploration area valuation and the locations of wells for prospecting drilling.②study every index in MPOG on forecasting hydrocarbons accumulating.③classify the anomalies in MPOG.④made the suggestions for the future exploration.The mechanics of MPOG is:light hydrocarbons migrate predominantly vertically from deep reservoirs up to surface soil driven by "microbubble buoyancy", which provides favorable conditions for obligate bacteria, i.e. hydrocarbon-oxidizing bacteria (HCO),and results in great increase of number and activity of HCO and then anomaly zones. On the basis of these zones, the existence and characteristics of underground reservoirs can be appraisable and predictable.In this paper,the practical programs of MPOG are expounded, such as field geological survey and sample collection, microbial experimental technique, data process and assess criteria, comprehensive evaluation and potential prediction of oil and gas, etc.Field geological survey and sample collection is base on the difference of exploration aims and the degree of knowledge in geological structure. when we general investigation in the areas, sample collection distance usually deign500m or1000m. when we have some knowledge about this area, sample collection distance usually deign under250m. In study area, sample collection distance is250m×250m.Microbial experimental technique is evaluation the quantity of microbial. In order to evaluate microbial anomalies, we adopt a suit of assessment index-MU value. It contains the quantity of microbial(n), activity(a), microscope assay results(o), earths surface humidity(t), sample humidity(h), lithology(l), color(c), PH value(p)and earths surface vegetation(v).Data process and assess criteria is base on microbial analysis report, geology structural map, two or three dimensional seismic map. Study microbial anomalies area is correspondence with the location of geology structural, location of oil well and reservoir’s characters and it exploration history, microbial anomalies is correspondence with existence achievement. Last, give the well design.Based on anomaly detection of micro-organisms, it can be evaluated and forecast oil and gas underlying the existence and nature of possession. Thus it is suitable for gangxi area.In the study microbial abnormalities technology for oil and gas assisted identification of reservoir area of westen end of gangxi structure, collect1353samples, about80.0km2in total. After this area microbial abnormity analysis, we finished microbial assisted identification hydrocarbon zone.The thesis based on the abnormity of micro-organisms, combined with regional geological data, prospecting results of drilling and logging, etc, having carried out an analysis of micro-organisms in an anomalous region of the studied area, and delineation of ten obvious anomalous zones. By the detailed discussing to the measuring point number, maximum value, average value, shape and area oil anomaly which is involved in each anomaly area. With which the oil and gas prospecting zones are ranked to three, at the same time the optimal target area, the general enrichment area and somewhat less enrichment area are designed. It is that A anomalies zone is the most beneficial exploration zone, B anomalies zone is optimal target area, C anomalies zone is the less beneficial exploration zone.Based on the classified rank of the microbial anomalous zone, through the faults, sand body distribution, productivity distribution, and compared with abnormity of adjacent areas, detailed analysis of the hydrocarbon potential of the studied area was conducted.Microbial exploration is reflected in the outcome of plane distribution of oil and gas reservoirs. It reflects the superposition results for the reservoir with several sets. The studied area was oil rich banded scattered, not even the formation of high-value area. The anomalous mean of anomalies is not high, that means this area with little amount of oil filling, and small oil layer thickness. The gas anomaly is mainly showed as the background value. The faults are not developed or the accumulation of oil and gas are not controlled by the faults. There is no larger structure to form an effective trap either. According to the distribution regularity of oil and gas under the studied area, that the studied area scattered distribution of reservoir are lithology reservoir mainly controlled by sand bodies, is likely to be the shallow reservoirs with low porosity and low permeability. This type of reservoir has small structural traps locally, but the controlling area is small, oil and gas injection is inadequate. And it is characterized by a reservoir with a little top gas, non-pure gas reservoir.The microbial prospecting for oil and gas (MPOG) technology was applied to the western end of Gangxi structure, Studied57microbial parallel samples, we validate the repeat and dependability. To study depth how to influence microbial abnormity, we choiced60referene points, and get that the number of microbial are most in the0.6m depth. And discovered twelve microbial abnormity zones,12abnormal area classification:an abnormal area for the most favorable-rich region, four abnormal area is generally rich region, seven anomalous zone for the poor-rich region. The work area gas is generally low outliers, and did not form a contiguous gas reservoir anomalies similar to the distribution law and the oil; exception with the oil most of the basic coincidence, the oil and gas layer.