Getting good acid diversion in high water cut wells is always a challenge. Relative permeability effects due to high water saturations will push the aqueous base treating fluid into zones with high water cut. This leaves the oil zones untreated and results in dramatic increases in post stimulation water production.. While many fluid diversion techniques exist, this paper focuses on the successful application and results of a novel Viscoelastic Surfactant (VES) based fluid used as diverter in matrix stimulation treatments performed by CNOOC in its Java Sea, Indonesia wells. Introduction CNOOC in the Java Sea of Indonesia produces wells that are completed in both sandstone and limestone formations. Various completions methods have been employed including standard perforated completions, slotted liners, gravel packs, frac packs, and expandable screens. After the initial completion, the primary problems encountered in both sandstone and limestone formations are reduced production rate due to high water cut, and associated scaling. The primary production mechanism is natural water drive. Some of the fields also have water injection for pressure maintenance. The wells are generally completed over long intervals with multiple sets of perforations (see Figure 1). Most of the major platforms were developed in 1980's since then the reservoir pressure has declined by 50% to 70% (from +2000 psi to from 350 to 750 psi). Electrical Submersible Pumps (ESP) are used as the primary artificial lift method to maximize productivity from these high water cut (50%–98%)/low bottomhole pressures (350 psi-750 psi) wells. High water cut and scale deposition can result in rapid decline in flowing bottomhole pressure and production rates. If not treated in timely manner, the resultant drop in production rate results in ESP failures and costly workover operations. Acid stimulations are frequently carried out to remove damage and keep production above the ESP running limits. In most cases, wells are stimulated without pulling the completion (with the ESP installed). This reduces the cost of the workovers as well as reducing the dependence on the workover barges. The presence of an ESP in hole limits the diversion options during a stimulation treatment. Foam and polymer base fluids were previously used to achieve diversion. The results of these treatments were mixed and usually resulted in higher water cuts. It has to be theorized that the water cut increases because of relative permeability effects. In most cases, water has a lower viscosity and higher relative permeability than oil. When an acid treatment is performed, more of the aqueous treatment fluid will flow into the water zone then oil zone. Thus the bulk of the damage removal occurs in the water zone and even though the oil rate might increase, the increase is overwhelmed by the increase in water. So the key to stimulating these high water cut wells is to develop a method for diverting the acid away from the water zone into the oil zone. Without adequate diversion, high water cut and lower sweep efficiency are often the result of a stimulation treatment.

RINGKASANHidrosol adalah produk samping distilasi minyak atsiri. Dalam dunia industri, keberadaan hidrosol tidaklah diperhatikan untuk rendemen minyaknya. Hidrosol merupakan cairan emulsi dari minyak yang terikat oleh molekul air. Dalam penelitian ini, hidrosol dipisahkan dengan tujuan untuk mendapatkan minyak yang dapat meningkatkan rendemen minyak atsiri.Pemisahan hidrosol dilakukan dengan metode elektrolisis. Dengan adanya elektron yang mengalir dari anoda, diharapkan agar tegangan antarmuka dari minyak dan air dalam hidrosol dapat terpisahkan. Metode elektrolisis dilakukan kimia minyak hasil elektrolisis. Minyak hasil distilasi diuji dengan GC-MS untuk dijadikan sebagai pembanding/standar. Elektrolisis hidrosol dilakukan dengan 3 (tiga) variabel, yakni jenis elektroda, waktu elektrolisis, dan besar tegangan. Optimasi dilakukan dari perlakuan eletrolisis hidrosol yang optimal. Minyak hasil elektrolisis diuji kembali dengan GC-MS dan dibandingkan dengan standar untuk melihat kualitasnya.Hasil elektrolisis menyatakan bahwa jenis elektroda yang paling baik adalah seng. Waktu elektrolisis optimal dengan menggunakan seng terjadi pada waktu 60 menit dengan besar tegangan 20V. Minyak hasil elektrolisis dengan elektroda seng hasil optimasi memberikan kualitas minyak yang lebih baik dari minyak hasil distilasinya. Hal ini dinyatakan secara kuat dari kadar patchouli alcohol dalam minyak hasil elektrolisis yaitu 36,40%, sedangkan dalam minyak hasil distilasi yakni 33,46%. Kadar patchouli alcohol mengalami kenaikan hingga 0,08%.