Study Repeat Facturing Technology In AnSai Oilfield

Ansai oilfield, located in the central eastern Ordos basin, is the first exploration and development oil area of the monolithic and low permeability oilfield in China, and is also a typical siliclastic reservoir with low to very low permeability, low pressure, and low-yielding. The wells were taken fracturing production in order to obtain industrial oil flow in the past years. The initial fracturing was gradually failuring and oil well production declined characterized by blockage, resulting in different dynamic oil production capacity and yield poor results in part of the main lateral wells, via waterflooding conventional measurements, as oil well production time passing. Thus repeated fracturing stimulation must be proceeded for these wells in order to improve well production. The geological characteristics, distribution of fissures, nature of fluids and dynamic oil production of the Chang6pools of Yanchang Formation, Upper Triassic from AnSai Oil Field is investigated and analyzed in this thesis. Reservoir plugging mechanism and parameters influencing increasing single well oil production is discussed. Changes of magnitude and orientation for geostress are determined, via experiment of core fracturing crack test and by theoretical analysis. Possibility of repeated fracturing to generate new joints, exploration of repeated fracturing mechanism is verified. The much better scientific model for selecting wells and layers thus shaped, by using fuzzy pattern recognition model and method of gray correlation analysis. The repeated fracturing of wells and layers, focused on selecting fracturing fluids and proppant, temporary blocking agent are studied, and optimizing parameters in the ongoing process of implement are analyzed, thus the more perfect repeat fracturing technology is formed, which has become the major stimulation treatment for old oil fields.