Northeastern Sichuan Dam Area Gas Drilling And Formation Water Study

The Heba area of noutheasten Sichuan possesses abundant nature gas, but the shallow and middle formation has the characters of high degree hardness,worse abrasivity,week drillability, more circulation loss that causes low rate of penetration, long-term drilling, and brings difficulty to the exploitation of gas.As a result of that air drilling can boost the rate of penetration greatly, shorten the term and reduce the cost of drilling, air drilling has been used widely in this area. Whereas in the process of drilling, the shallow and middle sand shale formation yields water seriously, it challenges the construction of air drilling.This research takes the sand shale formation of Heba area of noutheasten Sichuan as the object, it starts with analysing rock constituents, calculating volume content and physical property parameters, identifying fluid nature.With that it carries out the works including estimating layer of yield water, analysing pore pressure, establishes the model to calculate the amount of yield water and composes a relevant software.This research utilizes several methods to identify fluid nature including three porosity overlay method,neutron-density curve overlay method, three porosity ratio method,φ-Sw crossplot method, orthogonal doublet array acoustic logging analytic method and so on, they can help recognizing the layer of yield water more exactly. This research according to the basic theory of fluid mechanics in porous medium,connecting the practical condition, analyses the yield water from four occasions;it divides the water yield formation to two occasions just water layer and gas water layer to build the models separately. What is more, this research workout a software to calculate the amount of yield water which based on the theory model of bit drilling out water layer. It used simply and conveniently,comparing the result with practical data, the effect is feasible.The upper series of research aims to form a suit of pragmatic forecasting technique to yield water for air drilling in Heba area and then forecast potential layers and amount of yield water for future air drilling in Heba area according to logging interpretation and processing drilled wells,it still provide these potential layers with relevant settlement and subject.which is the base to carrying out air drilling smoothly, enhancing the wellbore quality,shortening the term and reduce the cost of drilling,it still provide a necessary guarantee with accomplishing excellent and rapid drilling and rising the exploit efficiency in Heba area.