Research On Low-permeability And Thin Reservoir Development By Horizontal Wells

The purpose of this paper is to effectively develop marginal oilfields with low abundance, low permeability and thin reservoirs using horizontal wells. The horizontal well technology study includes accurate structure interpretation and inversion using 3D seismic data, 3D geological model building, reservoirs prediction, horizontal well design optimization, analysis while drilling, completion mode design optimization and modification of well pattern based on methods of accurate structure interpretation, inversion, geological model building, reservoir simulation, lab experiment and analysis with drilling, etc.. The achievements are as follows:The structures of top and bottom of Putaohua I formation in the area of horizontal well are interpreted using 3D structure interpretation and 3D geological model building, structure models are built by well region, and the micro- structures feature of subdivisions are accurately described with error less than 1‰.The distribution of reservoirs have been predicted accurately using seismic wave impedance inversion and lithology prediction, stochastic model building controlled by sedimentary microfacies integrated with seismic data, sedimentation facies, cores, well log data to fit in thin reservoir with strong heterogeneity and to use it to the thin reservoir less than 1m .The geological models including fine structure models, sand distribution models and property models are built to describe structure feature and reservoirs'properties to characterize heterogeneities by stochastic model building using the results of structure interpretation, inversion, and facies study in horizontal area of Aonan field.The heterogeneities of thin Putaohua reservoirs including sedimentation, permeability, lithology, sand distribution and sand body connectivity are recognized to further knowing reservoirs.Horizontal wells are suitable to develop thin reservoirs of Aonan field by feasibility evaluation of horizontal wells including reservoir type, reservoir property parameters, and technical & economical limiting of horizontal well development. A set of parameter optimization method of horizontal well suitable to low permeability and thin reservoir characters have been built. Horizontal well design has been optimizated and good drilling results have been gotten.Horizontal well analysis while drilling and adjustment in thin reservoir have been built and applied including geology model building, LWD, formation correlation, oily property analysis of sand bodies by integrating geology, reservoir engineering, drilling engineering and well logging to assure success of horizontal wells with 68% ratio of sand to horizontal section.The horizontal well completion programs have been studied to get optimum horizontal well completion mode in thin reservoirs using heterogeneous geologic model building and reservoir simulation and get 2 to 5 times average production rate of horizontal wells than those of vertical wells.Based on reservoir feature and sand body correlation relationship, well pattern have been evaluated, the character of horizontal wells under water-flooding, the principle and method of injection and production adjustment, and development results have been studied under various strategies of water injection of various injection pressure, injection-production ratio.Based on multidisciplinary study and application of horizontal wells, a set of integrated oilfield development study and design method of horizontal wells have been formed to suit specially low abundance and low permeability & tin reservoir, helping horizontal wells to be applied to development of thin reservoir with strong heterogeneity and less than 1m thickness, and increasing production rate of individual well and recovery factors of oilfields to economically develop thin and marginal reservoirs with low abundance and low permeability.