Improved calculation models for penetration ability of deep-penetrating horizontal perforation technique with self-induced nozzle bit

Abstract

High-pressure water jet deep-penetrating horizontal perforating (DPHP) technique is one of the most effective ways to enhance the oil recovery, and the extreme perforation penetration affects directly the effect of oil recovery. But the calculation model of perforation penetration ability of DPHP has been rarely researched and calculation results of the existing calculation models have large errors with the actual data, which are insufficient to provide effective support for DPHP operation. In this article, with consideration of initial momentum of drilling fluid in jet bit, DPHP system force analysis model has been established and friction coefficient between hosepipe and horizontal perforation has been obtained in laboratory experiment. An improved calculation model for length of penetration is established based on the DPHP system force analysis and relevant calculation models for frictions. Influential parameters of penetration length like flow rate of drilling fluid, specifications of hosepipe, and structure parameters of self-propelled nozzle are investigated by this improved model. The research results show that the perforation penetration ability of DPHP is positive to the drilling fluid flow rate and the flexile hose ID. The number of forward nozzles and the angle of backward nozzles need to be minimized in order to meet rock-breaking and expanding ability of self-propelled nozzle, and both the number and diameter of backward nozzles should be optimized. Drilling parameters of DPHP field test in PG oilfield are designed by employing this model. Maximum extension capacity is 31 m, and the error is 8.5% compared with the prediction result 33.6 m of the new simplified model. However, prediction result of the existing model is 12.8 m with an error of 58.7% compared with actual extension capacity, which manifests the accuracy of this model.