T he “P-1S” gas well is located in Field P, Banyuasin Regency, South Sumatera Province which was completed at early July 2006. Analysis results of a Drill Stem Test conducted at July 21-24th 2006 yielded a positive skin, and “P-1S” gas well was then stimulated through matrix acidizing to improve its productivity. A second Drill Stem Test was conducted at July 28-30th 2006.This Final Assignment was done to evaluate the effectiveness of the matrix acidizing job in repairing the well’s formation damage, which was done by analyzing the pre and post acid Pressure Build Up tests and deliverability tests. The Pressure Build Up test analyses were done through pseudopressure Horner manual calculation and through Ecrin software using the pressure derivative method. And the deliverability analyses were done through Rawlins-Schellhardt manual calculation and using Ecrin software. Before acidizing, Pressure Build Up analysis through Horner plot yielded a permeability of 227 mD and skin of 354; while Ecrin software pressure derivative analysis yielded a permeability of 211 mD and skin of 355. The post-acid Horner analysis yielded a permeability of 258 mD and skin of 6; while Ecrin software pressure derivative method yielded a permeability of 257 mD and skin of 5. The Ecrin model used pre and post acidizing was a homogeneous reservoir model with one fault boundary, and a limited entry well model with a changing wellbore storage. The deliverability analyses results showed a significant increase of well productivity after acidizing; where the acidizing job increased the QAOFP from 20 MMscf/D to 350 MMscf/D.