Abstract: A well fluid sampling tool and method for retrieving single-phase hydrocarbon samples from deep wells. The sampling tool is lowered to the required depth, an internal sample chamber is opened to admit well fluid at a controlled rate, and the sample chamber is then automatically sealed. The well fluid sample is immediately subjected to a high pressure to keep the sample in its original single-phase form until it can be analyzed.The sample is pressurized by a hydraulically-driven floating piston powdered by high-pressure gas acting on another floating piston. Once sampling is initiated, e.g. by an internal clock, the entire sequence is automatic.Also disclosed is a sample transfer container for securing the pressurized sample from the tool and maintaining it in single-phase form during transport to an analytical laboratory.This invention avoids the disadvantages arising from phase separation of hydrocarbon well fluid samples.