Research On High-quality Reservoir Prediction Of Low-porosity And Low-permeability Sandstone Gas Reservoirs In The Huagang Formation Of X Gas Field

The Huagang Formation in X gas field is a typical low porosity and low permeability sandstone gas reservoir.H3 is the main gas stratum of Huagang Formation,with the high sandstone content and the thick single sand body,showing a relatively stable spatial distribution.However,the reservoirs in the main layer show strong heterogeneous,and there are large differences in productivity between different layers and adjacent wells.At present,the understanding of the study area only stays at the level of sedimentary facies.The understanding of the main reservoir and the distribution of high-quality reservoirs is not studied well.Above of all,the development target cannot be hit accurately,and the well deployment lacks reliable guidance,which greatly limits the development efficiency of gas reservoirs in the study area.In this study,the third section of Huagang Formation of X gas field was used as research object.Under the guidance of sedimentology,seismic sedimentology,reservoir geology and geostatistics,combine the of drill core,well logging,seismic data and dynamic data to predict the distribution of high-quality reservoirs.Establish the sequence stratigraphic framework and then elaborating the sedimentary microfacies of the target stratum and clarify the reservoir characteristics.After that,build a well logging-lithology prediction model and a seismicsandstone/high-quality sandstone thickness fitting model with the method of well-seismic integration.The main layer sedimentary microfacies distribution is constructed by the two prediction models.Under the guidance of depositional mode,the spatial distribution of highquality reservoir in H3b-2 and H3b-3 has been predicted and a series of achievements have been made:1)The sequence stratigraphic framework of study area was built,and the target layer was divided into three sand formations and seven small layers,of which H3b-2 and H3b-3 small layers were the main productive layers in this study.2)The target stratum is braided delta front,and six types of sedimentary microfacies are divided into underwater distributary main channel,underwater distributary secondary channel,underwater distributary channel wing,channel bar,channel bar wing and underwater interdistributary bay,so as to make clear the spatial distribution of sedimentary microfacies.3)Combining with the petrological characteristics,physical property analysis and pore characteristics of the reservoir,the medium-sandstone facies in the tabular cross-bedding and the parallel bedding are determined to be the best lithofacies.Combining with the sedimentary mode,the medium-sandstones and fine-medium sandstones in the channel bar are confirmed to be high-quality reservoir.4)The spatial distribution characteristics of high-quality reservoirs in the main reservoir are predicted by using the method of well-seismic integration under the guidance of depositional mode.High-quality reservoirs are mainly developed in the lower part of H3b-3,followed by the lower part of H3b-2.In the plane,the high-quality reservoirs are mainly distributed in the northeast of the gas reservoir,followed by the middle of the gas reservoir.H3b-3 is superior to h3b-2 in terms of the plane distribution range,thickness and lateral continuity of the high-quality reservoir,which should be the paid more attention as primary target of further exploration and development.This study accurately predicted the spatial distribution of high-quality reservoirs in the third section of Huagang Formation of X gas field,which not only provided an important and reliable basis for the delineation of target in further exploration and development of X gas field,but also enriched the method and theory for predicting high-quality reservoirs in low porosity and low permeability sandstone gas reservoirs.Offshore oil field often has fewer wells,which restricted by the cost of drilling.The study used the methods of well-seismic integration,multiparameter fitting method to achieve the high-quality reservoir prediction,solved the problem of inaccurate reservoir lateral prediction due to the lack of well control.Accurately depicting the distribution of the high-quality reservoir in low porosity and low permeability sandstone,provided the significant instructive theoretical basis of the high-quality reservoir prediction and efficient development in the similar offshore oil and gas fields as well.