CASE HISTORIES    

Field Example 1 :

Enhanced production by allowing a certain amount sand production:

We helped CNPC to design their sand producing well in oversea field. Screen was implemented inside casing for sand control. A production rate of 41 m^3/day in average was obtained. Based on our COMPUTING s, a 5-8 times production increase can be obtained if we allow a certain amount sand can be produced, yet such a sand production will stop after a certain period of time. Re-completion gave CNPC more than 150 m^3/day for all four trial wells, major surface construction and pipeline design were implemented afterward. Such a sand rate COMPUTING proves to be vital for a company to forecast their productivity and related engineering design such as production and surface transportation. Not only they received local government approval for the project, but they expect a much higher production and profit. The theoretical background and some discussions can be found in JPT and SPE Formation Evaluation 2002 by Wang and Chen.

Field Example 2:

 Predicting onset of sand production: extensive onset sand prediction services provided to Elf Aquetaine, CNOOC, UNOCAL, PETROCHINA, etc. .

Case #1 : Elf Aquetaine

The onset of sand production for deviated gas well was the major concern. In their field, more than 70% wells were facing this issue if these wells are producing sand, as at least $150,000.00 USD would be required in each of these wells if sand control is required. Our studies confirmed that perforating with a certain angle against the in-situ stresses can reduce sanding risk.

Case #2 : CNOOC

In their off-shore reservoir, 33 wells were in production and 3 of the wells were already producing sand which were forced to be closed. Using the data from the 3 sand producing wells, we successfully predicted the other 30 wells. Among these 30 wells, only 2 wells which were predicted to produce sand at a later stage of production produced sand at the very beginning of the production, all other 27 wells did not produce sand within the predicting range.

Case #3 : UNOCAL

A large oil reserve was planned to be developed in the next two years. Our AGENTS  wanted to evaluate the realistic productivity as these formations contain multiple pay zones and some of them are poorly consolidated. Foot-by-foot examination and prediction indicated that the weak formation is located in a certain depth, a isolation for this zone during production is necessary in order not to produce sand yet maintain a high production. UNOCAL adjusted their production and surface operational plan according to our critical production rate prediction.

Field Example 3:

Sand prediction for well completion screening for horizontal well

Two cases are presented here one for Petrochina on shore and one for CNPC oversea project. Petrochina owns a high-rate oil reservoir which has been in a high-rate production. Since 2004, a production declining plan was forced in as sand wuold have been produced if a certain drawdown was exceeded. Gravel packing was proposed in some of the wells, a minimum production reduction of 25% were forecasted based on SAND_PRO. A 200 meter long horizontal well was recommended by PGI, and a similar production level was maintained afterward, yet no sand was produced. The CNPC oversea project was similar to the Petrochina case, except CNPC’s reservoir is much more thin. There are two pay zones in this region, however the deeper pay zone which has less productivity was selected for production as this higher productivity formation were facing more sand production. Sand control was proved to be more costly with less production, a horizontal well was also recommend based on SAND_PRO COMPUTING s, which led to a sand-free producing horizontal well.

Field Example 4:

Producing Oil with Massive Sand Production

This is a typical Northwestern Alberta case, where our focus is to manage the sand rate for oil enhancement. Both an erosion model and wormhole models were used for this field case, cumulative sand production and the enhanced productivity were matched with the field history. Several SPE papers on these field studies and discussions can be found in PGI’s website.