Abstract
An important issue in the functioning of a production system, including a productive formation, a wellbore zone, a well and wellhead equipment, is the preservation of the natural filtration-capacity properties (FCP) of the productive formation. During well drilling, under the influence of a pressure drop in the "well-formation" system, the filtrate of the drilling fluid used in drilling enters the bottomhole zone of the well (BHZ) and the FCP deteriorates. Deterioration of the formation permeability even at an insignificant distance from the well wall leads to a noticeable decrease in production. The issue of the optimal choice of process fluids used in drilling is of great importance. The drilling fluids used, in addition to solving the problems of preventing fountaining, removal of cuttings, elimination of absorption, must prevent damage to the wellbore zone of the formation. Foam systems and hydrocarbon-based solutions (HBS) have found their application in industrial practice to solve these problems. To assess the ability of solutions, including HBS, to retain weighting agent, the Sag Factor (SF) is used. At values , it is considered that the solution is capable of retaining the weighting agent. Absorption is caused by the influence of a large number of factors, which makes it difficult to identify patterns and select effective measures for prevention and elimination. The determining approach is to reduce the density of the drilling fluid. To reduce the time for eliminating absorption, temporary isolation of productive horizons is used when washing in fillers, such as: viscoelastic compositions, non-hardening cement mixtures, quick-setting compositions. Opening and inducing an inflow into a well is an important stage of well construction, determining the flow rate and service life of the well. Well development is often accompanied by complications, both geological (low values of the reservoir properties, high viscosity of oil) and technological (pollution of the productive formation during the initial opening by components of the drilling mud, solid phase and filtrate, cementing, perforation) reasons. Traditional methods of inducing an inflow are based on reducing the pressure in the well by reducing the density of the liquid or its level; if no inflow is observed, then methods of development in difficult conditions are used. In carbonate rocks, hydrochloric acid treatment (HAT) is recommended to clean the bottomhole formation from clay crusts, mechanical particles and filtrate of the drilling fluid. Hydraulic fracturing is used to create highly conductive fractures that ensure the flow of produced fluid to the well bottom. In recent years, hydraulic fracturing has been carried out in both low-permeability and high-permeability formations. One of the complications in the development of late-stage deposits is the water cut of well production. A possible cause may be the presence of behind-the-casing flows, which are caused by poor well casing. Measures to isolate aquifers are carried out in three directions: selective isolation of water inflows during repair and isolation work, improving the quality of well casing, and temporary blocking of the formation. Development of an oil reservoir composed of weakly cemented sandstones is often accompanied by sand removal into the well. The reasons for sand removal are: the presence of unconsolidated sand, exceeding the maximum permissible depression, migration of small particles. Research conducted by academician A.Kh. Mirzadzhanzade showed that the destruction of sand arches in the formation also occurs at depressions below critical in the presence of fluctuations in the filtration rate. The fight against sand production is carried out in two directions: preventing (chemical, combined, mechanical) and reducing sand removal (technological and preventive). Preventive measures include washing the sand plug. The issue of deciding on the need to wash the sand plug is relevant. The sand plug in the well can be in a suspended (pseudo-liquefied) state or in conditions of predominant sand sedimentation at the bottomhole. In the first case, there is no significant impact on the flow rate. The use of dynamic systems methods allows diagnosing the condition of the sand in the well and making an informed decision on the current repair of wells. Keywords: drilling of wells, filtration and capacity properties, productive reservoir, operational complications, well repair.
Published Version
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