Jilei Niu

Abrasive Water Jet Perforation—An Alternative Approach to Enhance Oil Production

Abstract This article investigates the mechanisms, the results of laboratory experiments, and the results of field tests on the abrasive water jet (AWJ) perforation for enhancing oil production. The mechanism investigation showed that the AWJ perforation is a two-stage process, the ductile casing erosion stage and the brittle rock penetration stage, and each stage follows different failure mechanisms. The laboratory AWJ-parameter experiments were conducted on pressure, flow rate, abrasive material, abrasive granule size, abrasive flow rate, ambient pressure, rock material, and exposure time. The field tests of 10 oil wells (11 runs) illustrated that the AWJ perforation depth could reach about 0.78 m with pump pressure of 45–60 MPa at different formations, while the location error was less than 0.1 m. The oil production rate comparison, before and after implement, showed the AWJ perforation technology can effectively and prominently enhance oil production.

Hydraulic Pulsed Cavitating Jet-Assisted Drilling

Abstract How to improve drilling rate in deep wells has been a hot subject. Based on modulating pulse jet and cavitating jet, a new drilling tool is designed which couples advantages of both pulse jet and cavitating jet. When drilling fluid flows through the tool during the drilling process, fluid is modulated to pulse and cavitate. Thus, pulse cavitating jet is formed at the outlet of the bit nozzle. Because of jet pulsation, cavitating erosion and local negative pressure affect bottomhole rock. Cleaning and breaking is enhanced and penetration speed is improved. Oil field tests in five wells show good applicability of the tool to bit types, formation, drilling densities, flow rates, and dynamic hydraulic drilling motors, etc. As a result, penetration rates are improved ranging from 10.1 to 31.5%; the maximum working time is about 235.5 hr in downhole. Pulse and cavitating jet coupling will afford an effective means to improve drilling rate for deep wells.

Investigation and Application for Multistage Hydrajet-Fracturing with Coiled Tubing

Abstract Continuing high prices for oil and gas stimulate new technologies improve the production of low permeability reservoirs. Hydrajet-fracturing with coiled tubing, a unique technology for low-permeability horizontal and vertical wells, uses fluids under high pressure to initiate and accurately place a hydraulic fracture without packer, saving operating time and lowering operating risk. The mechanisms of hydrajet-perforation and hydrajet-fracture initiation are studied in this article. Frictions for one kind of fracturing fluid in coiled tubing have been computed to determine pump pressure and flow rate for field testing. Tools for hydrajet fracturing are designed as well. The first successful field testing in China of multistage hydrajet-fracturing using coiled tubing has proven that the theoretical calculation and field-testing data of hydraulic parameters are basically identical. It has also proven that tools meet the requirement of field testing.

STUDY OF TREATMENT OF NEAR WELL-BORE FORMATION PROCESSED WITH HIGH PRESSURE ROTATING WATER JETS

ABSTRACT High pressure water jet removing impurities in formations is a new way developed recently to increase oil production and injected-water. First of all, this paper presents the main reasons of formation plugging, the basic principles of high pressure rotating water jets removing impurities and the laws of the tools rotating speeds, impact pressure and relations between impact pressure and nozzle stand-off. The field-test results obtained from over 500 oil and water-injection wells in Liaohe, Shengli, Zhongyuan, Huabei etc., indicate that this technology has such advantages as simplicity of use, cost effective, high success rate, wide adaptability, and significant effectiveness. From this, it is profitable and promising to increase production in highly water-cut oilfields.

Surface Experiment of Abrasive Water Jet Perforation

Abstract This article presents the experiment process and results of abrasive water jet perforation. This experiment was conducted in Kalamayi, China, Xinjiang Oilfield in October 2004. Referring to explosive perforation experiment, we made two cement cylinder samples with a diameter of 2.4 m, 1.2 m high, putting a 139.7 mm (5-1/2″) and a 177.8 mm (7″) casing sub in them, respectively. The two cylinders were buried underground. During the experiment, we changed the following parameters: blasting time, nozzle diameter, and cement cylinder property. After experiment, we opened the cylinder and found that, compared with explosive perforation, the hole on the casing wall and the tunnel in the cement were much rounder and bigger than with that method. In addition, it can cause a fracturing effect, possibly forming micro-fractures on the tunnel wall. This effect can avoid forming impermeable crushed zone when using explosive perforating.

Application of Abrasive Water Jet Perforation Assisting Fracturing

Abstract This article presents a new technology of abrasive water jet perforation assisting fracturing on Well Zheng 408-8, Bin Nan Production Plant, Shengli Oilfield. First, the balsting tool, with 9 nozzles, was lowered down to the payzone and perforated 90 tunnels with abrasive water jet after being moved upward 9 times. Then the fracture work was conducted and 18 m3 sands were squeezed into the formations. After that the well production reached 11.6 t/d liquid and 8.7 t/d oil, respectively, and this continued for 9 months. But before the job, nothing was produced from this well.

Enhancing Oil Production by Helical Hydraulic Sand-Blasting

Abstract The helical hydraulic sand-blasting slotting technology is a new development of the traditional hydraulic sand-blasting slotting technology. The original nozzle gun movement control system was replaced with a helical slid rail, and thus the application was extended to directional and horizontal wells. Experiments were conducted to study the feasibility abrasive water jet slotting sand prevention tubes. The effects of slotting were compared before and after the slotting implementation for 10 wells, five production wells, and injection wells, respectively. The results show that: (1) To succeed at sand prevention tubes slotting, nozzle movement must be smooth and very slow to avoid discontinuous, isolated holes; (2) At 30 MPa or higher, the slotting technology could generate slots of 700–1,000 mm deep; and (3) Besides the benefits of enlarging the oil and gas seepage area, the slotting technology could increase the reservoir formation permeability reasonably.

Self-Excited Oscillating Water Injection: Mechanisms and Experiments

Abstract This paper briefly describes the working principle of the self-excited oscillating nozzle and the experimental results of the pressure impulse characteristics and its frequency distribution under different ambient pressures. The transmitting law of the pressure fluctuation is introduced along the casing in both the axial and the radial directions. In addition, it presents the principle of water-injection with self-excited oscillation, the designation of the injection tool, and the field experimentation results. The field results indicate that the self-excited oscillating cavitation jets can be used as an effective way to prolong the production period of the well because the jets minimize formation block up. The average injection pressure was reduced by 2.1 MPa, and the averaged volume of daily water injection for a single layer increased by 29 m3. It can also prolong the water injecting time of the general water-injecting well.

An Experimental Study of the Sealing Mechanism During Hydrajet-fracturing Treatment

Hydrajet-fracturing technology depends on a jet stream to achieve a seal for stimulation without mechanical devices. An experiment combined with a numerical simulation method studied the sealing mechanism. It found a low pressure field around the jetting tool and the head of the cavity. Because of the pressure regime, high pressure fluid in annulus will flow to this area and then mix with the jet stream into the fracture. Research showed that three factors influence the sealing pressure. This value will become larger with the jet pressure and nozzle diameter rising. The casing hole plays a seal role to prevent the cavity pressure from disturbing the sealing pressure. Based on the experimental data, a model of sealing pressure is proposed. Microseismic monitoring results prove that treatment fluid is effectively isolated into every fracture for extension. The conclusions and models are significant to further understanding of the hydrajet-fracturing process.