Loose Sand Reservoir Damage Mechanism And Its Application To HND-1/2 Oilfields

This paper analyzed the internal and external reasons for the formation damage of the loose sandstone reservoir in the process of drilling, completion, producing and workover in HND-1/2 oilfields, the damage mechanism has been determined, and the optimized stimulation measures have been taken out, the main measure is defuse plugging. With the emphasis on the aspects of mechanism, experimental research, implementation process scheme, construction scheme, effect assessment, etc., the acid defuse plugging technology and the biological enzymolysis plugging technology have been analyzed systematically. And, typical application examples have been analyzed, and the stimulation scheme for the similar wells have been carried out.The experiments of oil reservoir permeability space, rock mineral, rock surface properties, inner environment, rock strength, stratigraphic expansion and cation exchange capacity and other related experimental research of HND-1/2 oilfields show that particles migration and wetting reversal potential damage exist in these oilfields. These damages were induced by incompatible working liquids sucking into the formations, which were used in the process of drilling, completion, workover operations. The new mechanism of solid phase block up damage of loose sandstone reservoir has been carried out. During the production process, the solid phase particles adsorbed the heavy components of the producting fluid, so, the particles were wrapped to be the visco-plasticity solid phase. As the content of the heavy components increased, the adsorption ability of the reservoir rock surface was strengthened. So, the solid phase jammed pore throats, the formation permeability and the production rate were declined. For one thing, the viscosity of the mixed fluid is higher than that of the crude oil, and was enhanced by the solid particles, the existence of solid particle enhanced the produced liquid emulsification degree, the stability of emulsion liquid.For another, the particle migration speed also was intensified by the viscosity increase.Based on the quantitative analysis of skin factor, the main reasons of the formation damage were determined. And, this paper illustrated that the acid defuse plugging technology and biological enzymolysis plugging technology are the effective measures for the defuse plugging for the similar HND-1/2 oilfields loose sandstone reservoir damage.On the basis of the acid dissolution experiment, acid additives single-item experiment, iron ion stabilizer performance evaluation experiment, the retrofit silicic acid and multi-hydrogen acid system was optimized as the acid liquid, and the field application in the wells HND-1-A9, A10, A7 showed that the increasing production effect was obvious. Through the experiments of developing enzyme stability test, removing heavy components pollution experiment, removing drilling fluids, The conventional characteristics and removing ability from enzyme heavy components pollution of the filtrate Apollo has been studied, and the field application in well HND-2-A9 showed a great success, the production rate was 16 cubic meters per day. And on the basis of the experiments reffered above, a set of reservoir damage mechanism research, production plan and implement process scheme and effect assessment has formed, which can provide guidance for the similar oilfields domestic and abraod.