Liaohe depression is famous as rich of oil and gas resources in Bohai Bay Basin. Even though the exploration degree of Liaohe Depression is relatively high, some favorable effect is also made in exploring burial hills, volcanic rock and lithologic reservoirs under the guiding of the theory of petroleum-rich and persisting in thinking innovation. Fromthe aspects of thought innovation, cognition change, enhancing acquisition of high quality seismic data,developing dominant technique,perfecting management,successful practice and experiencemade in LiaoheOilfield exploration have been discussed.

Based on the discussion of exploration course, distribution features of volcanic oil reservoirs in Liaohe Depression and these oil reservoirs' characteristics, the reservoiring mechanismof volcanicoil and gas reservoirs has been concluded as follows: structure condition would be thekey factor, oil source might be the base and lithologic condition can be as important complementarity. The exploration technologies, include seismic pattern recognition, log distinguish, lithologic identification, lothologic-facies analysis, reservoir prediction and fracture prediction technologies, have been concluded. Taking the volcanic exploration of eastern sag in LiaoheDepression as an example, the effect of exploration and development of volcanic reservoirswas analyzed.Up to the present, the important breakthrough hasbeen made in entire volcanic rocks in eastern area, discovering trachyte and dolerites oil reservoirs. InwhichHuangshatuo oilfield belongs to trachyte oil reservoir,has been built the reserves level often thousand-ton and formed certain production capacity. Through further exploration, some cases' result analysis reflect that the volcanic gas reservoirs have big potential and promising prospects for exploration and development,whereit ,asoil/gas explorationfrontiers, is worthto paya special attentionin the future exploration

The breakthrough has been made in burial hills exploration in Damintun Sag through deepening geologic cognitions, changing the idea of exploration and developing technology for burial hills exploration since 2000. It summarizes systematically the main exploration ideas in burial hills, DamintunSag,sets up the formation modeof oil/gasreservoirs,concludes thetechnology characteristicsof burial hill exploration,analyses the exploration results and exploration practice achieved in recent years and points out the next prospecting targets

Starting with analyzing the exploration status of oil-gas reservoirs in western sags of Liaohe Depression, it is thought that the western sags have entered into high mature stage of exploration,after the origins ofvarious-type lithologic reservoirs in western sags were studied, but there is still a considerable potentialfor lithologic oil reservoirs to explore.On the basis of summarizing on distributioncharacteristics of variouslithologic reservoirs, it is pointedout that, the majorfuture exploration fields should be turned to lithologic reservoirexploration fromstructural reservoir exploration,and the next exploration targets will focus on the following areas, i.e.Yuanyanggou-Qijia area, the downthrough side of Taizhuang-Dawa fault, Dongying Formation in Qingshui sag,Xinglongtai-Maquanzi burial hills belt and burial hills belt in western slope

Controlled by the factors including anticline, fault, sedimentary cycle and sedimentary facies, four oil-bearing horizons series of the 1st member of Shahejie Formation, the 1st,2nd and 3rdmembers of Dongying Formation developed in Taiyangdao -Kuihuadao structural belt frombottom to top.Vertically, oil-gas reservoirs are characterized by the gas-bearing layers developed in the top and the bottom, and oil formation developed in the middle part, that is to say, gas reservoir mainly formed in the middle-upper part of the 2ndmember of Dongying Formation, oil-gas reservoir mainly formed in the lowerpart of the 2nd member of Dongying Formation,the thicker pure gas reservoir developed in the 3rd member ofDongying Formation. Based on the study of organic evolution history and the configuration of faulting movement, trap forming and oil-gas migration, the result shows that three stages of reservoir forming had occurred in the study area, namely, early stage of reservoir forming occurred in the end of the 1st member of Shahejie Formation deposition, mediumstage of reservoir forming occurred in the end of Dongying Formation deposition, the late stage of reservoir forming occurred during a period fromGuantao Formation toMinghuazhen Formation.This area stillhas a relatively big potentialityboth vertically and horizontally,which result fromthemulti-stagereservoir-forming anddifferential migrating and accumulating.Several promising traps such asTaiyangdao structure,Kuihuadao structure, faulted nose in the easternKuihuadao, and faulted nose in the western Kuihuadao, are determined through study

Several great breakthroughs have been made continuously in Damintun sag in recent years, the discoveries, including Anfutun,western Dongshengpu and Pinganpu burial hills,have been regarded as the typical examples of deepening exploration formature oil-producing areas. Practical experiences madein exploration showthat changing the idea of exploration is precondition, innovation and development of exploration technique is key factor.Aiming at the key geologic difficulties such as complicated structures, reservoirs recognition and evaluation,fracture developed or not and area predictionof lithology,integratedexploration technique series ,consisting of 3-Dvisualization,seismic multi-attribute,integratedwell logging evaluation, multi- attributeinverse of reservoir characteristicsand etc,have been developed ,which has played a keyrole in launching integrated evaluation,guiding drilling distribution and discovering newoil belts and fields.

Due to the special condition of seismand geology in Liaohe Basin, the predominant frequency of seismic data collected in deep strata before concentrated around 20-25Hz.These old seismic data has become the"bottleneck"of exploration work in Liaohe area,which has restrained the further exploration and development of LiaoheOilfield.To meet the fine structure interpretation and oilreservoirs description requiring for seismic data, Liaohe Oilfield tackled the key problemusing a series of acquisition methods in Damintun area, formed a completed fined 3-Dseismic acquisition technique, which is applied and made better effect in secondary collecting.

The volcanic oil reservoirs are characterized by lowpermeability, deep burial depth, tighter rocks, thickoil-bearing intervals and developed natural fracture and solution pores, and which have some difficulties such as high temperature of reservoir, high pumping pressure, high fluid loss, high fracture initiation gradient and high rate of sand up while fracturing.Aiming at the mentioned features above, it is determined the main guiding thinking of large drainage volume,medium-lowratio of sand and creating long-fracture to makemuchmore fractured fissures formand communicate with natural fractures and solution pores as far as possible, so as to realize the goal of forming oil flowpathway. The volcanic fracturing technique, mainly characterized with anti-high temperature, anti-high pressure, anti-sand up, reducing fluid loss, dropping opening and fast back drainage, has been formedand popularized widely on-sites to raise largely the success rate and availability in volcanic fracturing construction ,while alsomake the effect of increase reserves and output well

In recent years,though considerable commercial oil-gas flowwas discovered in all kinds of carbonate,volcanic rock,metamorphic rock and lowresistivity sandstone strata,howto usewell logging datato continue to find oil and gas reservoir in high efficiently andmore accurately,and howto evaluate water-flooded oil bed are still very difficult.According to the complicated features of various-type oil-gas reservoirs in LiaoheOilfield,it is discussed the well loggingseries relatedto several complicatedoil-gas reservoirs,and evaluated differentoil-gas reservoirs byusing sufficiently richwell loggingdata and advanced technology,and got niceapplication effect.

According to the geologic features ofLiaohe Oilfieldand to meet the demandsof exploration and development,Si-Fl mudhas been developed and applied to 330 wells in 27 blocks. The application results showit is characterized with stable property in high temperature, high ability to prevent fromcollapse, low mineralization degree and low fluorescence,so it can meet the requirement to deep exploration and increase drilling velocity and reduce accidents and complicated situations to protect oil-gas layers

NuclearMagnetic Resonance mud logging(NMRmud logging) is a technique that mainly applies the CPMGpulse sequence to measure transverse relaxation time(T2) , its size and distribution in hydrogen pit that exists in rock samples, acquire reservoir's physical parameters timely and accurately while drilling.The feature of NMRmud logging is that the cutting analysis has its own particular characteristic,andis free fromthe limitation of sample types,moreover, the analysis speed is quick,and an analysiscan not only provide many parameters but gain precise analysisresults.NMRmud logging has been used for more than one year in Liaohe exploration area, playing an important role in assessing reservoir and interpreting oil, gas and water layers,having certain significance for exploration in oilfield.

During the drilling process, it is difficult to collect the log data when the cave-in takes place.KCl drilling mud is one of the methods to protect side-wall fromcollapsing, nevertheless it reduce the response of log curve to strata characteristics and is not favorable for well log evaluation. Based on the actual data ofLiaohe Oilfield, it analyses the property of KCl mud,studies the influence of KClmud to resistivity curve,GRspectrumcurve and GR curve and the correction methods for GRcurve, discusses the way to eliminate these effect, and provides the evidence to KCl mud logging evaluation.

As the exploration targets become increasingly complicated and the exploration is more and more difficult, exploration information has become the importantmanner to promote the development of core exploration business and reduce the exploration cost. Through more than two years ' construction of exploration information,Liaohe Oilfield has formed the complete systemof exploration information, and regularize the management rules and standards of exploration information, and forms initially the "three-level" database systemincluding special database, central database and project database for exploration information management. The remarkable effect has been made in systemconstruction and database construction.This information systemhas played an important role in exploration and gained good effect in oilfield

More than 30 years splendid history has been experienced ,the serious prospectingand development situation of natural gas has been facing by Liaohe Oilfield.With the production ofmajor gasfields turning into the late phase ofdevelopment, and stored resources becoming severe shortage, it has beenmore difficult to maintain the stable production.The prospecting direction and objectives of natural gas during the period "11th-Five-Year Plan" is analyzed. The favorable measures to natural gas exploration and development in Liaohe Oilfield include the transformation from"main gas-bearing intervals "to"subtle gas-bearingintervals",thechange fromonshoretobeacharea,the conversionfromconventionalreservoirsto subtle andunconventional gas reservoirs,much attention to be paid for finding the potential of mature area, finding effectively newresources substitution.